Mr. Manning is murdered in his study while the door is locked from the inside. Police close the case after 6 months. A girl contacts Charlie Chan to have a look before he leaves in 48 hours. Twins are involved in a diamond-smuggling ring after the Kohinoor Diamonds are stolen; one twin is killed and the other living twin masquerades as a ghost tricking Birmingham Brown. Mr. Manning had the largest stone stored in the secret compartment of a Chinese cat statue, and doublecrossed his associates. Movie ends in a carnival funhouse with police arresting the diamond-smuggling ring for three murders. Rival author of ''Manning Murder Solved'' book must now pay $20,000 to Chinese War Relief after a lost bet with Charlie Chan about the murderer's identity.