Murder Has a Motive - Francis Duncan

A classic Golden Age mystery perfect for fans of Agatha Christie's Hercule Poirot
When Mordecai Tremaine emerges from the train station in the village of Dalmering, murder is the last thing on his mind. But he has never been able to resist anything in the way of a mystery—and a mystery is precisely what awaits him in the small hamlet.
Rehearsals for the local amateur dramatic production are in full swing, but as Mordecai discovers too soon, the real tragedy is unfolding offstage. The star of the show has been found dead, and the spotlight falls on Mordecai, whose reputation in the field of crime-solving precedes him.
With a murderer waiting in the wings, it's up to Mordecai to derail the killer's performance...before it's curtains for another victim.
Mordecai Tremaine Mystery Series:
Murder for Christmas (Book 1)
Murder Has a Motive (Book 2)
So Pretty a Problem (Book 3)