Wealthy diamond collector Larry Hanrahan is given the opportunity to assist the beautiful, jewel-bedecked woman he admires in a Broadway café when she and her guardian are attacked by robbers. Larry is invited to visit the grateful pair, Col. Paul Gascoyne and his ward Adrienne, at the colonel's laboratory, where he is introduced to Wintermute, a chemist who produces imitation diamonds. In return, Larry asks them to view his priceless diamond collection. Although he has fallen in love with Adrienne, Larry is forced to believe that she is a thief when he is robbed by a woman wearing Adrienne's scarf. Larry finds his jewels in Gascoyne's house, but before he can escape, a group of thugs overpowers him. Adrienne assists him in contacting the police, who arrive in time to capture Gascoyne and his gang. Badly wounded, the colonel confesses that Adrienne has been his innocent dupe, whereupon Larry happily takes her to his heart.

• Mystery
• Crime