Biggers, Earl Derr - Keeper of the Keys

Source: Wikipedia

Keeper of the Keys (1932) is the sixth and last mystery in the Charlie Chan series of Earl Derr Biggers; Biggers was planning on continuing the series, but died in 1933 before he could.

Once again, the setting of the novel is California, where Chan has been invited as a houseguest. He meets a world-famous soprano, who is murdered not too long after the meeting. Once again, Chan is expected to solve the murder, which he does in typical fashion. One of the strongest entries in the series, with a clever trick used to trap the murderer at the end.