Detective Steve Harrison receives a mysterious note urging him to meet at Storley Manor, promising information about a man named Richard Stanton. As he approaches the isolated and dilapidated mansion, he narrowly escapes an assassination attempt. At the manor, Harrison, pretending to be a stranded motorist named Buckner, is welcomed by the owner, John Storley, who lives with his purportedly disabled uncle William Blaine, the housekeeper Rachel, and a laborer named Joab.

Harrison quickly senses underlying tension and danger within the household. During dinner, he declines a potentially poisoned drink and later discovers a snake placed in his room to kill him. His investigations are interrupted when he receives a warning note, leading him to suspect that not all is as it seems with the Storley family and their servants.

Under the guise of darkness, Harrison meets Storley, who reveals that he himself sent the original message and that Stanton is hiding nearby. Storley advises caution as they are dealing with dangerous people. However, before more can be revealed, Storley must return to the house, fearing for his own safety.

The plot thickens as Harrison discovers that William Blaine, previously thought to be disabled, is neither blind nor deaf. Tensions escalate when Joab, driven by past crimes and manipulations by Storley, attacks Harrison but is fatally subdued by the detective.

As the night progresses, Harrison learns from Rachel, who has been brutally beaten and left for dead, that Storley has turned homicidal, having attempted to murder a young man—the real Richard Stanton—who has now lost his memory. Harrison rushes to save Stanton from Storley's final attempt to kill him at a remote cabin rigged with explosives.

After a dramatic confrontation where Storley accidentally kills himself with his own booby trap, Harrison and Stanton piece together the motives behind the murderous schemes. They realize that family ties and hidden identities linked to a significant inheritance were driving forces behind the violence.