At P Division headquarters in Washington, General Bart Brookstone summons Lieutenants Benjamin Ader and Max Redhorse to his office for a briefing. He informs them that a priceless ancient Babylonian artifact, the Eye of Al N'Set, was stolen from the Persian National Museum of Antiquities not long ago. Legend records that The Eye, dating from at least 2060 BC, is used for scrying and distant vision, and that it foretold the Babylonian king Ninus of his conquest of Assyria in 2059 BC. Brookstone informs them that P Division is working in cooperation with the Persian Department of Relics and Antiquities in its investigation of the crime. He is assigning the two men to track down a man suspected of involvement in the case, a sinister American fellow known as Elias Kingsley. He hands them a photo and profile of Kingsley, along with a picture and information about The Eye of Al N'Set, and tells them to prepare to leave for Arkham, Massachusetts, Kingsley's last known location.

Meanwhile, in Arkham, the Amsbary siblings, Julia, Megan, and Jeremiah, receive an unexpected package in the mail. It is from their uncle Abner in Boston. It is a box containing a long letter, an ancient document, and a bizarre pair of goggles with a couple of sets of removable lenses. The letter says:

August 2, 1920
My Dear Children,
I cannot tell you how deeply I wish things could be different, but they cannot. In this box you will find a gift. It is your inheritance. It is your destiny as Amsbarys. For all the world I wish I could give it to you personally, and explain it to you personally, but that is now probably impossible. ...I hope you can forgive your old uncle and remember him with kindness.
This box contains a family treasure that has been passed down, in secret, for generations. They're called Hosiah's Spectacles. They were built by your great great great grandfather Hosiah Amsbary in 1807. Originally, there were three sets of lenses, but your grandfather, my father, destroyed one pair in 1871. The two surviving pairs are also included. The spectacles must be treated with care. They are old and fragile as you can see. ...

The letter goes on to tell the whole story of how Hosiah Amsbary was plagued by bizarre dreams throughout his life and found the meaning of those dreams in the world of the occult. It tells how he travelled to Europe at the turn of the 19th century, and found some crystal lenses in Romania, and how he returned and, with his two brothers— who also had the dreams and knew of the occult—built the spectacles and developed a three-man ritual to use them. It tells how the brothers looked through the magic spectacles they had created, and saw into other dimensions. In time, they all saw the same bizarre visions they had seen in their dreams, and they all became very powerful wizards. And it tells how the spectacles have been passed down secretly from generation to generation ever since Hosiah's death in 1820.

Abner describes his own experience with the spectacles, how they enabled him to see a city he had seen in his dreams, and how they gave him peace of mind. He quotes his Aunt, who had the spectacles before him, as saying: "I've been looking at the world all my life, but I never saw anything until I looked through Hosiah's Spectacles."

Abner goes on to warn the children that sometimes one sees things through the spectacles that one would rather not. Some members of the family, he tells, have gone mad after looking through the glasses into other dimensions. But, he reassures them, the spectacles are only windows to the invisible: nothing can come through them to "get" you. If you don't like what you see, close the blinders and stop the vision.

The letter ends this way:
...I've told you what the spectacles are, and where they came from, and all the history I know. I've told you they're a good thing not a bad thing. I've warned you to be careful with them. I've told you what I know to help you make them work. There's only one thing left to explain, and that's why I'm sending them to you now. Your Aunt Madeleine wanted to pass them on right after your father died, but I told her you were all too young and not ready. Of course no one has worn the spectacles since then. For five generations, more than a hundred years, Hosiah's Spectacles have been the treasure and the secret of the Amsbary family. Those of us entrusted with the spectacles have even kept them secret from our children, wives, mothers and husbands. No one but the three initiates and their forbears knew they existed. Until now. I do not for the life of me know how it happened, but somehow someone has found out about them. A man approached me a few days ago and offered to buy them. He offered me 250,000 dollars. I was in shock. I told him I didn't know what he was talking about, that there were no spectacles. But I was so upset it must have been obvious I was lying. Anyway, he didn't believe me. He told me knew all about them and would pay handsomely for the spectacles, both sets of lenses, and any extant papers by any family member about them. I told him he was crazy. I insisted I didn't know what he was talking about. Then he threatened me. He said that he would get the spectacles one way or another, and that he'd give me a day or two to "see if I could find them."
His name was Elias Kingsley. About my age, well-dressed, gave me a visiting card. I don't know anything else about him. ...He came by here again this afternoon. I told him there were no spectacles and that I wanted him to leave me alone. He was very civil and said he was sorry we couldn't do business. His friendliness today was more frightening than his aggressiveness Tuesday. I believe that he is planning something desperate. I very much fear that by the time you receive this I will already be dead. I hope not. Maybe I'm imagining it. Maybe I convinced him. But I very much doubt it. I feel fairly certain he plans to take the spectacles and that he will murder me in the process. He would have to. I'd die sooner than let him get them. That's why I'm sending them to you now, and why I'm writing instead of delivering them in person. I'm sorry it had to be this way.
I beg you children to sign Hosiah's will under your father, Aunt Madeleine and I, and take your rightful place in Amsbary history. ...I send you the spectacles and charge you with their protection.
...One final thing. If I am not dead, I will be in touch with you very soon. If I am dead, it might be possible for you to see me through the spectacles. Having passed over to the other side, I would be invisible to the normal eye. But through the magic lenses I could have become visible. Dead or alive, I will come to Arkham and try to leave you a message. Look for me. I will be trying to reach you, one way or another, I will get another message through. Don't try to reach me in Boston. I don't want Elias Kingsley to have any help finding you. I'm sorry it has to be this way. Forgive me. Take care.
Love,
Uncle Abner

The crumbling, ancient document included with the letter is Hosiah Amsbary's will, written in 1824. It gives a brief explanation and history of the spectacles, couched in terms of mysticism and dreaming. A central passage reads:

The Amsbarys dream. Our father before us was plagued with visions of the larger world, and my brothers and I have searched, and we have glimpsed the universe. When I found the crystals, I knew how they could be used. Through the spectacles we have seen what is normally invisible.
The spectacles are like windows through which one can see other aspects of what is. Through them you can see other parts of time, other parts of space, other states of being. Each set of lenses works differently; each person sees through the spectacles differently.
Valentine and Samuel have passed on and I grow old. I have seen you, my children, struggle with your dreams. I know you perceive more completely than ordinary men. I have decided to pass the spectacles on to you, so that you too may see, and learn. Donning the spectacles is a serious and unretraceable step. It will change your view of the world forever. Be not afraid: be careful.

The will goes on to describe the three-man ritual in detail, and tells exactly how to use the spectacles. It ends with an appendix added later by Hosiah's children:

We take these spectacles as our own and vow to keep and guard them, and use them well, until we pass them down to our children, in the name of our father, Hosiah Amsbary.

Beneath the passage are the signatures of twelve Amsbary descendants, including, at the bottom, Abner Amsbary.

The Amsbary siblings are overwhelmed by these revalations, and are reluctant to believe the outlandish tale the letter relates. But, they each confess that they have had bizarre dreams all their lives, and the story does strike a chord with all of them. Julia attempts to call Abner in Boston, but there is no answer. She gets in touch with the Boston police force, and is horrified to learn that her uncle has, in fact, been murdered. The police inform her that his mangled body was found in his home, and that a strange blue substance left behind has so far been unidentified. The police say they'll contact the family when they have more details. The Amsbary children, stunned, look over the package Abner sent them, and, after some debate, sign the will and study the spectacles.

Meanwhile, Ader and Redhorse have arrived in Arkham, and go to Vriner's restaurant, the last reported location of Elias Kingsley. They sit in a booth there for quite some time, eating, drinking, and supposedly looking out for Kingsley. He never shows up. After a long time and a complete meal, they begin to question other people in the restaurant, showing them Kingsley's photograph. A man at the bar says that he recognizes Kingsley, and writes an address on a matchbook. They leave.

Going to the address supplied by the man, they spot Kingsley going into an apartment building. They check out the mailboxes, trying to figure out which unit Kingsley might be occupying, but don't reach any conclusions. They sneak into the building, trying to find him, and see him leave an apartment. They follow him at a discreet distance. However, since they're both wearing all-black uniforms, they're incredibly easy to spot.

They follow Kingsley as he walks across town, watch him pick a flower from somebody's garden, until he eventually arrives at someone's house. Kingsley goes up to the front door and rings the bell. A woman answers, and after a brief conversation, he goes inside. Ader and Redhorse watch the house while Kingsley is inside.

The house is that of the Amsbarys, and inside Kingsley introduces himself to the frightened Amsbary children. They have hidden the spectacles and all the papers, and when Kingsley tells them that he knows about the spectacles, feels sure they have them, and offers $400,000 for them, the Amsbarys tell him that they have no idea what he's talking about. He loses patience relatively quickly, saying that he hopes they won't be as stubborn as their uncle, thereby implying that they will be killed if they don't cooperate. They hold their ground, however, and Kingsley leaves uttering thinly veiled threats.

Outside, Ader and Redhorse see Kingsley leaving, and decide to follow him again. They leave.

Inside the house, the terrified Amsbary children decide to try to contact Uncle Abner by wearing the spectacles. Julia, the eldest, is elected to be the one to wear the bizarre contraption, and after consulting the will and learning the correct procedure, she puts them on.

Her experience is quite strange. Through the spectacles she sees the room, but her vision of it is highly distorted and fragmented. She seems to be able to see more of it, as well, as though her field of vision has been increased by 180 degrees. Once she and her brother and sister concentrate on Uncle Abner, he appears to Julia. He seems to be speaking, but she cannot hear him. He stands in the room, looking as he did in life. He holds out a book with a red cover, and Julia also sees an image of the Miskatonic University library. Abner holds the book toward her and gestures at it. She describes the vision to her siblings, and attempts vainly to speak with Abner. Abner then removes a large knife from his clothing, and, gesturing to Julia to remain calm and watch, he rolls up his sleeve. Julia begins to panic, not liking what she thinks her uncle is going to do, and her brother and sister try to calm her down. Uncle Abner, after a brief pause, cuts his wrist with the knife, and the blood flows copiously over the book that he is holding. Julia continues to watch only with great difficulty. Once the book is drenched in Abner's blood, he holds it up to her and gestures at it. The image of the library reappears, and then the entire vision is gone. Julia still sees the distorted image of the room in which she stands, but nothing else. Deeply shaken, she ends the ritual and removes the spectacles.

Meanwhile, Ader and Redhorse have followed Kingsley back to the apartment building. After staking it out for a short time, they decide to return to the Amsbary home and question the occupants.

Back at home, the Amsbary siblings discuss the possible meanings of Julia's vision. Is this the message Abner promised in his letter to send? Megan wants very badly to look through the spectacles herself. She points out that different people see through the differently, and believes she might be able to get more clear directions from Uncle Abner. Julia and Jeremiah agree, and repeat the ritual with Megan wearing the spectacles. Her experience is a total failure. She sees bizarre images of nightmarish creatures, and gets no additional help. After a terrifying experience, she shuts the blinders.

Just then, a new knock comes at the door. The Amsbarys quickly hide the spectacles and all the papers and timidly answer. It is Ader and Redhorse. The Amsbarys let them in, but have grown very paranoid and skittish. They don't reveal anything to them. They say they don't know who Kingsley is, and don't know what he wants. The lieutenants, for their part, suspect the Amsbarys of being Kingsley's accomplices, and therefore believe they are involved in the theft of the Eye of Al N'Set. Everyone can tell that everyone else is lying, and nobody trusts anybody else. Ader and Redhorse leave, telling the Amsbarys that it really would be best for them to cooperate.

The Amsbarys quickly decide that Uncle Abner was trying to tell them to go to the Miskatonic Library and look for additional information in a book. They're not sure which one, but they decide they'll go and try to figure it out at the library. They divide up the spectacles and the papers amongst themselves, and go to the library. Ader and Redhorse, who are spying on the house, follow them.

At the library, the Amsbarys don't know what to look for. They talk to a librarian, who seems rather nervous himself, and ask if he has any interesting red books available. Though initially quite hesitant, the librarian eventually confesses that as a matter of fact, a very strange red book was found in the library that very day. He tells of an ordinary book which was found mysteriously covered in blood. No one at the library can explain it. He has hidden the book in his office, and is reluctant to show it to anyone except authorized officials who could take it off his hands. He will let the family members look at it, but not take it away. The Amsbarys decide to ask Ader and Redhorse to intervene on their behalf. They meet them (in their black uniforms they're not hard to find), and after some tense discussion and give and take, they agree to work together. The librarian happily agrees to let the army men take the book away.

The book is indeed covered with blood. One page, in particular, is completely soaked, and has the words "RED LENSES" written in blood on one corner. In a private location, the Amsbary children take out Hosiah's Spectacles, insert the red lenses, and look again at the page. With the aid of the magic spectacles, they can read the message contained on the page. It says:

Children—no time—you must act quickly
Get helmet—amulet from Kingsley Hound coming— Grave peril—Amsbary hill tonight at moon zenith—Use Helmet—Spectacles—Amulet—Read Spell—Blinders Down— See Hound—Dispel—Make Haste—Beware—Farewell
Ai Ai Azathoth! Barra Barra na zu Absu! Ia kia kanpa barra barra

The Amsbarys still don't entirely trust the lieutenants, but they all decide to go back to the Amsbary house and decide how to proceed together. Returning there, they discover that someone has been there and has searched the house. Things are in disarray. As they take stock of the situation, Ader and Redhorse realize that the someone must still be in the house. While motioning the Amsbarys to continue talking as if nothing were happening, they begin to search the house. As they look into a hall closet, suddenly Kingsley bursts out. There is fight, and a gun goes off. Kingsley is dead. They search his pockets and find a set of keys.

As a group they go to Kingsley's apartment. It is almost completely empty. All they find is a small valise containing a number of extremely interesting items. The most notable is a bizarre black leather helmet with an odd nose guard. Also in the valise, wrapped in cloth, is a very strange and beautiful silver amulet: the Eye of Al N'Set. Accompanying the two items are numerous files and other papers with the company logo of New World Incorporated. One document reads:

Project Nº: 13B
Project Name: Amsbary Lenses
Report Nº: 13B20 S

Date: 2 August 1920

Status:
¶ First Meeting: NWI Subject Nº 36,301 uncooperative. Monetary offer refused. As predicted, subject denies knowledge and existence of lenses. Subject is asked and given opportunity to reconsider.
¶ Second Meeting: Subject remains uncooperative. As prediceted, professes ignorance. Subject behaves as per model. No progress expected.
¶ NWI Special Operative 5000 summoned to deactivate subject. Acquisition of NWI Item Nº 3864 to follow. Projected acquisition date 3 August.

A second document reads:

Status:
¶ NWI Subject Nº 36,301 deactivation by NWI Special Operative 5000 successful.
¶ Search of subject's home and known places of refuge have failed to recover NWI Item Nº 3864.
¶ Subject may have sent NWI Item Nº 3864 to NWI Subjects Nº 45775, 45776, and 45777. NWI Officer E. Kingsley will investigate. Problem minor. Expected resolution 4 August.

A handwritten report indicates that NWI Special Operative 5000 has been summoned to deactivate NWI Subjects 45775, 45776, and 45777, and that deactivation is expected to take place at midnight that very night.

A fourth report is most revealing. It reads, in part:

Project Nº: 13C
Project Name: Helmet
Report Nº: 13C5 IP

Date: 17 July 1920

¶ Construction on NWI Item Nº A5000 was completed here today at 6:39 P.M., according to specifications and research provided. Adjustments were made to accommodate NWI Item Nº 3807 when it became available to the design team. Further adjustments may be required upon acquisition of NWI Item Nº 3864. None are expec- ted, as provided information has been exceptionally thorough.
¶ Here follows a labelled diagram of NWI Item Nº A5000.
[A picture of the leather helmet]
NWI Item Nº A5000 is a matrix helmet, designed to work in conjunction with NWI Item Nº 3807 and NWI Item Nº 3864 to permit trans-dimensional coterminous physical access. The completed Helmet will combine the power of the Eye of Al N'Set and the Amsbary Lenses, allowing the wearer to physically travel and interact in dimensions visible through the lenses while simultaneously remaining in his own. The complete Helmet is a gateway to multi-dimensional operation.

Finally trusting each other, the investigators all pool their information and figure out what is going on. NWI stole the Eye of Al N'Set (Item Nº 3807) and wanted to steal Hosiah's Spectacles (Item Nº 3864) to use on their magic Helmet. Unable to get the spectacles from Abner, they summoned Operative 5000, which the Lieutenants speculate is probably a Hound of Tindalos, and killed him. They have summoned another Hound to kill the Amsbary children, and Uncle Abner has given them a spell to stop it. But performing the spell requires one of them to put on the helmet, complete with spectacles and amulet. They must wait until the moon is at its zenith, and after checking they discover that that won't be until late that night, just moments before midnight, when the Hound is due to arrive and kill them all.

Their course of action thus laid out clearly for them, they sit and learn the spell and prepare for nightfall.

That night, they all go to Amsbary Hill, a blighted bump out on the ancestral family land. Jeremiah is selected to wear the helmet, and the Lieutenants and his sisters strap him in, according to the diagram in Kingsley's files. They insert the Eye of Al N'Set in its special pocket in the nose guard, and attach Hosiah's spectacles in their proper place. When it is on, Jeremiah looks very strange. He and his sisters go out to the top of the hill, and do the ritual.

Through the Helmet, Jeremiah sees many bizarre things and has sensory experiences which he describes to the folks nearby. They cannot see the things he is describing. He is in another dimension. Eventually, he sees the Hound approaching from the distance. He describes it also. But this time, the others can see it. The Hound is entering their dimension as well. Jeremiah utters the spell given by Uncle Abner, and the Hound, after hesitating, is dispelled.

Jeremiah collapses, and seems to be nearly comatose. The Lieutenants carry him to the car, where he revives. The Amsbary children are reunited in safety, and the Lieutenants take the Eye of Al N'Set.