John Hammond`s partner, George Sullivan, dies in an apparently accidental death, with Hammond the beneficiary of his double-indemnity insurance policy. Since this is the fourth double-indemnity death in the Sam Marlo, California vicinity in recent months, the company assigns investigator Tom Davison to the case. The partner`s daughter, Nancy Sullivan, cooperates with Davison in the investigation, and Davison joins Hammond`s business as a salesman. Davison is closing in on the gang, led by Chuck Malone, when the gamblers behind the racket kill Hammond, making it appear as a suicide to protect themselves. Davison gets conclusive evidence against the gang when they kill another man for his insurance, but the mob kidnaps Davison.