This screwball detective story about several people trying to get a valuable horn was loosely adapted from a novel by Dashiell Hammett.
Detective Ted Shayne (William Warren) is put on a train by city officials. He recommends the Ames Detective Agency to a woman, then goes to the office to take her call; she hires Ames (Porter Hall) as a bodyguard, enabling Shayne to re-hire unpaid secretary Miss Murgatroyd (Marie Wilson). Shayne is greeted warmly by his old flame Astrid Ames (Wini Shaw). Valerie Purvis (Bette Davis) hires Shayne to find her boyfriend. Shayne takes Murgatroyd out but has to go to a cemetery, where police found Ames dead. The gunman Farrow is shot there too. Astrid cries on Shayne's shoulder. Shayne learns that Valerie is leaving and joins her in a cab. He asks why she wanted Farrow shadowed, and she says Farrow did kill Ames. Valerie snatches back the $500 Shayne took from her purse and pulls a gun on him. Police Lt. Pollock learns that Valerie visited Farrow. Travers (Arthur Treacher) tears apart Shayne's apartment and comes back to ask for his horn. Travers retains Shayne for $500 and tells the story of Roland and his horn of jewels. Shayne finds his office torn apart too and lets Murgatroyd out of the closet. While Shayne tells her the story, Kenneth (Maynard Holmes) steals Shayne's case.
Shayne arranges to meet Valerie at a hotel so that he can search her apartment; but she surprises him with a gun. Shayne tells her the horn is related to the murders, and he searches for it. Kenneth takes Shayne to see his boss Madame Barabbas (Alison Skipworth). Shayne tells her he is working for Valerie, Travers, and himself. Barabbas hired Travers and Valerie to bring her the horn from Greece and offers him $100,000 for it, giving him $2,000. Shayne gives her the gun he took from Kenneth. She tells Kenneth he can kill Shayne after she gets the horn. Since Valerie is paying for protection, Shayne assumes she has the horn. He dances with her and asks her where it is. Four city fathers call on Shayne and demand he find Ames' killer in 24 hours. Astrid invites Shayne to dinner. Shayne goes to a boat in the rain and sees it burning. On the dock Kenneth shoots two men. Shayne takes Barabbas' gun and hits Kenneth with a horn. Shayne offers it to Barabbas, but Valerie asks for it, offering half. Barabbas says that Valerie betrayed Travers, the dead Espinoza, and Farrow. Shayne says that Travers killed Farrow and Espinoza, but he denies it. Kenneth says he killed them both, and Shayne plans to turn him in. Shayne gives Barabbas the horn for cash, but they find sand in it. Shayne turns Barabbas in to the police, Kenneth for murder and also Travers. Valerie and Shayne get on a train. They accuse each other of killing Ames; but Shayne gets Valerie to admit it. Shayne then gets the police and says three men are already dead for her. Finally he plans to have fun with Murgatroyd.
A tone of mockery pervades this absurd story of murder in order to get an 8th-century horn, offering the intrigue of a detective story while at the same time spoofing the genre.