In London in 1915, moneylender William Sharsted visits the home of one of his clients, an old man named Gingold. Inside, Sharsted admires Gingold's collection of rare paintings and suggests that the old man sell them. Gingold isn't interested and Sharsted turns the conversation to the 300 pounds that the old man owes him in three days.
The elderly collector refuses to discuss his debt and offers Sharsted a glass of sherry. He then leads the moneylender into a room with a table and an elaborate arrange of prisms and lenses. Sharsted dismisses the mechanism as a Victorian oddity, but Gingold explains that it's a camera obscura, which uses lenses and mirrors on the roof to project images of the town inside the room onto the table. He demonstrates the mechanism, impressing Sharsted, but then focuses the lenses on the home of a Mr. Thwitt. Gingold notes that Sharsted financially destroyed Thwitt with his interest rates, but Sharsted insists that it was a legal transaction. The old man says that what may have been legal wasn't just, and Sharsted says that he forced Thwitt to sell his home to pay his debts. He warns Gingold that he can force him to sell some of his beloved paintings to pay his debts, but Gingold condemns Sharsted for his lack of humanity.
Sharsted reminds Gingold of the money owed, but the old man invites him to examine another camera obscura, the only one of its kind. Sharsted agrees and Gingold leads him through a concealed panel, up a flight of stairs, and through a maze of corridors to another viewing room. This time the images displayed are those of London of 25 years ago in 1890, including the Corn Exchange, which burned down when Sharsted was a boy. As Gingold scans the town, Sharsted recognizes his father's pawnshop, which burned down years ago. However, the moneylender dismisses it as a trick using old slides and prepares to leave. Gingold gives him what he says is a last chance to reconsider collecting on the debts of his clients. When Sharsted refuses, Gingold tells him goodbye.
As Sharsted makes his way out through the corridors, he passes through a door and finds himself outside. The city is immersed in a greenish fog, and Sharsted has trouble recognizing the streets. He tries to summon a taxi without success, and asks an elderly lamplighter if there are any in the vicinity. As they talk, Sharsted notices that the lamp is gas, despite the fact that gas hasn't been used in 25 years. A horse-drawn cart goes by, and Sharsted notes that those haven't been used in years. When he turns back to the lamp, he discovers that the lamplighter has disappeared.
Sharsted continues walking and finds himself at the Corn Exchange, just as it was 25 years ago. A wagon pulls up and Sharsted finds the driver vaguely familiar. The driver knows Shalsted by name, and after a moment Sharsted recognizes him as Sanderson, a convicted grave robber who died in prison. Sanderson congratulates Sharsted on recognizing him and rides off, and the moneylender sees a corpse in the back of the wagon.
Sharsted runs down the street away from the Corn Exchange, only to find himself back at the same building again. The lamplighter is back at his lamp and laughs maniacally at Sharsted. Fleeing, Sharsted runs into Amos Drucker, a man he recognizes as his father William's partner. Drucker is a rotting corpse with a rope around his neck, and explains that he was convicted as a war profiteer. He hung himself rather than face trial and imprisonment.
Sharsted tries to flee only to return back to the exchange. His former partner, Abel Joyce, staggers down the stairs and confronts Sharsted, blaming him for his cheap funeral. Sharsted runs away down the road and Sanderson tries to run him down, and disappears just before he would strike Halsted. The moneylender finds himself at his father's pawnshop, and his father invites him in. Sharsted breaks the window glass and finds himself back at the exchange. All of the people of the city close in on Sharsted, who calls out to Gingold. The old man has watched the entire thing on the camera obscura, and declares that the moneylender will now spend eternity in his personal hell with his fellow leeches and grave robbers. Gingold places a cloth on the table and walks away as Sharsted is swallowed up by the crowd.