After Phyllis Fowler steals the "Blue Marquee" diamond from August Marino's jewelry store, Marino hires private detective Johnny Pierce to recover the stone. Johnny requires a $10,000 prepayment in order to begin work. Marino and his thugs trap Phyllis in her own apartment, but are unable to find the jewel. Phyllis escapes and Johnny follows her trail, but Marino does not trust the detective and sends two thugs to get to Phyllis first. The thugs are successful but Johnny recaptures the diamond from them and ostensibly gives it to Phyllis. In reality, Johnny has given Phyllis a worthless paste replica, which she takes to Queen City. Johnny catches up with Phyllis and learns from her that the "Blue Marquee" was stolen from her father, a legitimate jeweler. In Queen City, Johnny and Phyllis are entrapped by Marino's thugs and Johnny forces her to give them the diamond. Phyllis is disappointed in Johnny and is unaware that she gave them the paste replica; but Marino is outraged when he discovers the thugs' error. Marino tries to escape the authorities but he is captured by Johnny and arrested. The real diamond is returned to Phyllis's father, and Phyllis proves her renewed faith in Johnny by marrying him.