The A.B.C. Murders

Poirot is on the trail of an apparent alphabetical serial killer who sends an advance warning letter. Can Poirot, and his mismatched band of amateur detectives, solve the case before the killer comes to the next letter?
Quite a different style of novel from the other Poirots I've read but it works well. And yet again the Queen of Crime had me fooled until the end.