"A" is for Andover, the town where Mrs. Ascher is found battered to death. "B" is for Bexhill, where Betty Barnard is strangled. "C" is for Churston, the tiny Devonshire village where Sir Carmichael Clarke is murdered. Beside each body lies a copy of the ABC Railway Guide — open at the relevant page. The police are baffled. But the murderer has already made a grave mistake. He has challenged Hercule Poirot (David Suchet) to unmask him.