The Ex-Mrs. Bradford

Paula Bradford, a wealthy murder mystery writer, comes back from her travels to reunite with her former husband, Dr. Lawrence Bradford. She expresses her desire to reconcile and rekindle their relationship, despite his previous divorce due to her involvement in real-life murder cases. Their reunion sets the stage for the unfolding events.

A jockey riding the favorite horse suddenly dies while leading a race, which Paula becomes convinced was murder rather than an accident. The suspicious death prompts her and Mike North to investigate the circumstances around the event, suspecting foul play involving the race and the horse's death.

Dr. Brad finds traces of gelatin on the jockey's body, which puzzles him and suggests the possibility of a murder method involving toxic spiders. The inconsistency in the death raises further suspicion that the event was deliberately orchestrated, leading the investigation deeper into the racing community.

Brad receives an envelope at home containing a large amount of money, which he replaces with torn magazine pieces. Later, he gets a call supposedly from Mike North, instructing him to meet elsewhere without the money. These cryptic messages indicate a plot involving deception and hidden motives.

A burglar attempts to steal the envelope while Brad is away, leading to a fight. Paula intervenes, accidentally knocking Brad out in the process, which gives the intruder an opportunity to escape. This incident heightens suspicion and complicates Brad's efforts to uncover the truth.

Mike North's body unexpectedly falls into Brad's apartment, and Inspector Corrigan names Brad as the main suspect in North's murder. The police suspect Brad as he becomes entangled in the series of murders, forcing him to prove his innocence by solving the case.

Brad investigates various suspects including a bookie, a horse owner, and others connected to the racing world. Clues reveal that North made a clandestine bet and that some suspects had motives linked to the race and financial debts, opening multiple leads in the murder mystery.

Brad and Paula find the body of Lou Pender, who had posed as North, in a Murphy bed after he kills a spider. During the investigation, an unseen shooter targets Brad from the window, but he is not seriously injured, adding a new layer to the mystery.

Brad deduces that the murders are committed using gelatin capsules containing black widow spiders, which are attached to the victims' bodies. When the gelatin melts, the spider is released, explaining the method behind the killings and identifying a crucial clue in the case.

Brad anticipates the murderer will attempt another attack during the upcoming race and sets up cameras at the racetrack to catch them. His precautions include inoculating the jockeys to prevent spider bites, aiming to expose the killer during the race.

During the race, the killer attempts to strike again, but Brad's filming captures the act of Mr. Summers slipping a capsule down the jockey's back. The evidence confirms Mr. Summers' motive linked to revenge and personal grievances.

Confronted with the evidence, Mr. Summers admits to the murders, revealing his motivation was revenge against his unfaithful wife and her lover. Brad subdues him before he can harm others, bringing the case to a close.

In the aftermath of the case, Paula and Brad unintentionally cause Paula to knock out her ex-husband in a struggle. Despite the chaos, they reconcile and remarry, ending the story on a note of renewed love and resolution.