An investigator for the District Attorney's office quits to open his own detective agency. However, business is so bad that he finally decides to give it up and go back to his old job. As his wife is at his office closing up, a wealthy society matron walks in with a case: she wants to know if her husband is having an affair with his ex-girlfriend, who is now married. The wife accepts what looks to be an easy case, figuring than she can then persuade her husband to re-start the agency. However, when the client's husband is found murdered, she decides to investigate the murder herself. Her husband has also been assigned by the D.A. to investigate the murder, and he doesn't know that his wife is also on the case. Complications ensue.
Nick and Nora Charles investigate when Nora's cousin reports her disreputable husband is missing, and find themselves in a mystery involving the shady owners of a popular nightclub, a singer and her dark brother, the cousin's forsaken true love, and Nora's bombastic and controlling aunt.
Sir Borotyn, a prominent Prague resident, is discovered murdered in his home, with all indications pointing to a vampire assault. The victim's friend, Baron Otto, and the physician who analyzes the body, are certain that the vampire is the mysterious Count Mora or his daughter. Receiving little help from the law, Professor Zelen, an expert in the occult, is called in to assist with their investigation.
Investor Robert Norman murdered before meeting. Police investigate. Journalist Claire Haines pursues story to impress editor. Intertwining narratives of crime solving and reporting unfold.
In a spooky hotel on the coast of France, two bands of crooks are working independently of the other in an attempt to steal the inherited fortune of an American girl, Sue Tally. Along the way the heiress is kidnapped, three murders are committed, a girl appears in two places at once, mysterious persons roam about the old hotel at night and mysteriously disappear, and there is a hidden room without any doors.
As the demand for raw silk goes sky high, crooked businessman Wallace Myton corners the market with plans to drive up the price. Determined to fulfill his contracts, manufacturer Donald Kilgore imports $3 million worth of silk to Seattle and accompanies it by special train to New York. But when his secretary is found murdered, Kilgore soon discovers Myton has planted three killers on board with orders to stop the express and its passengers dead in their tracks.
Con-man Chandler and his partner Frank decide to start a clairvoyant act. Chandler falls for Sylvia, one of their marks, but their relationship is challenged when his deception impacts others' lives and Sylvia urges him to reform.
John Mason returns to the Sally Ann mine to claim his half share. Janet Cater also returns although her father lost his half share to Joe Ryan. Ryan and his gang are also there to get the gold. A mysterious Phantom is also present. Mason's plan to expose Ryan as an outlaw and to force him to turn his share to Janet works. But when distracted by the Phantom, John is made a prisoner by the gang.
Scion of the once-rich Mitchell family, Herbert Wynn is found shot to death. Nurse Adams, bored by hospital routine, is recruited by the police to ferret out clues as she tends to Wynn's elderly aunt Julia. Jokingly given the 'rank' of Miss Pinkerton, after the famous detective agency, Adams probes into the mystery, but not before a second death.
In 19th century Paris, a maniac abducts young women and injects them with ape blood in an attempt to prove ape-human kinship but constantly meets failure as the abducted women die.
Infamous burglar "The Bat" commits a daring jewelry theft despite heavy police presence. Soon after, a bank theft occurs, which may be the work of the criminal as well. Meanwhile, Cornelia Van Gorder has various people arrive at her old mansion, including her niece, Dale, a bank employee, and police detective Anderson. When guests start turning up dead, Cornelia begins to suspect that The Bat may be lurking around the estate.