The Plot Thickens (1936)

John Carter just had one of those days. First he had an argument with a mysterious Frenchman. Then Alice wants him to pick her up at the park after she has a fight with Robert over him. So Carter takes the roadster just as Marie and Joe were getting ready to leave. But Kendall, the butler, follows the roadster as he thinks it is Joe and his girl Marie. So when Carter picks up Alice and goes out in the country to park - he is shot dead. But the next day, he is found dead in the library at home. The investigation may be run by Inspector Piper, but most of the snooping is done by Hildegarde. The Sultan's Emerald, and a picture of the Cellini Cup, may be the clue leading to Carter's killer.