While watching from her train window, Nikki Collins witnesses a murder in a nearby building. When she alerts the police, they think she has read one too many mystery novels. She then enlists a popular mystery writer to help her solve the crime on her own, but her sleuthing attracts the attentions of suitors and killers.
Sherlock Holmes investigates when young women around London turn up murdered, each with a finger severed. Scotland Yard suspects a madman, but Holmes believes the killings to be part of a diabolical plot.
In 1903, Doctor Huntington Bailey meets a friendly older lady during a train trip. She tells him that she is going to visit her brother Nick and his lovely young wife Allida. Once in New York, Bailey hears that his train companion suddenly died. Shortly afterward, he meets the strange couple and gets suspicious of Nick's treatment of his wife.
Artist David Stuart is blinded by a jealous model whose portrait he is painting. His fiance's father generously offers his eyes for a sight restoring operation. There's only one hitch: Stuart has to wait until after the man dies. Not surprisingly, when the benefactor dies a very premature death, suspicion falls on the artist.
The famous Borgia Pearl, a valuable gem with a history of bringing murder and misfortune to its owner since the days of the Borgias, is brought to London, thanks in part to Sherlock Holmes. But before long the jewel is stolen, due to an error on Holmes' part, and shortly thereafter, a series of horrible murders begin, the murderer leaving his victims with their spines snapped and surrounded by a mass of smashed china.
An insurance representative is seduced by a dissatisfied housewife into a scheme of insurance fraud and murder that arouses the suspicion of his colleague, a claims investigator.
Stephen Neale is released into WWII England after two years in an asylum, but it doesn't seem so sane outside either. On his way back to London to rejoin civilization, he stumbles across a murderous spy ring and doesn't quite know to whom to turn.
When a woman is found dead with her throat torn out, the local villagers blame a supernatural monster. But Sherlock Holmes, who gets drawn into the case from nearby Quebec, suspects a human murderer.
Losing his memories of the last few days, neurologist Dr. Steele is told that his wife has been brutally murdered. Steele, aware of his conniving wife's infidelity, believes he may have been the killer and enlists the aid of his pretty nurse Stella to hypnotize him into recovering his lost memories.