Fiery nightclub dame Mary Dwight Strauber (Bette Davis) witnesses a murder at the Club Intime, but is terrified to testify against her slimy boss, notorious mobster Johnny Vanning (Eduardo Ciannelli). When Mary's innocent sister, Betty (Jane Bryan), gets mixed up in Vanning's racket and winds up dead, Mary finally yields to pressure from the District Attorney (Humphrey Bogart) and agrees to testify against Vanning in court, regardless of the death threats she receives from his henchmen.