The Suspense episode "The A.B.C. Murders" was adapted from the 1936 novel of the same name by Agatha Christie, but the radio version bears little resemblance to the original story. In the book, the mystery is solved by private detective extraordinaire Hercule Poiret, but Suspense's version leaves him out entirely. Instead, the story is condensed and uses only the basic plot from Christie's book.
As the episode opens, two librarians sit behind the counter and discuss the odd little patron who has just dropped off a book. Suddenly, they realize the man has left his briefcase behind. One of them, Franklin Clarke, catches up to the owner, and returns the case to him. The briefcase has the initials A.B.C. and the owner identifies himself as Alexander Bonaparte Cust. The two chat for a while and find out they have some things in common.
Later, Mr. Cust prepares to start his new job as a traveling salesman. His first stop is Andover, but what he doesn't know is that the police are in Andover warning the public about a homicidal maniac planning to strike in Andover. The same thing happens in the next town Mr. Cust visits, Bexhill.
He quickly becomes confused. Does he have something to do with the murders? With his terrible headaches, Mr. Cust sometimes doesn't remember what he does...
"The A.B.C. Murders" was adapted for radio by Robert Tallman and William Spier. Ted Bliss directed and William Spier produced. Charles Laughton starred. Also appearing were Elsa Lanchester and Bramwell Fletcher. This episode aired on May 18, 1943.
(Image of the first U.K. edition from Wikipedia)