Dancers in Mourning by Margery Allingham
My problem with Dancers in Mourning is that while the plot itself is well-done, Campion is not his usual self. He's over-emotionally involved and it's affecting his decisions and involvement with the case.
To start off, Campion visits the theatre with ‘Uncle’ William Faraday, who has found his mostly fictional memoir turned into a hit musical comedy. The star is dancer Jimmy Sutane, who is unsettled by a series of practical jokes and needs Campion's help. Campion and Faraday head to Sutane’s house, where they meet a group of theater/musical people. Not long after their arrival, another guest is dead, maybe accident, maybe murder, hard to tell. That's just the first of the deaths, there are three or four more before the killer is found.
Clearly, one of the people in the house is a murderer, and Campion has his suspicions. The problem is that Campion has fallen in love with Sutane's wife. I wish he hadn't. First off, he barely knew...