'Lyle Canvey, metallurgy, Arthur Stranack, mechanics, Rupert Eddis, chemistry, detested one another. This deep dislike was temperamental, admitted by each to be unjustified. They had not even the excuse of jealousy--each was proud of the others' achievements.' Three scientists who share a lock-keeper's house are all suspects in a murder. They work and live together yet they detest one another, but all detest their employer. It proves difficult to ascertain who is telling the truth and who is not. The police hear the same story from each man, but surely only one must be guilty of the murder, one must be aiding and abetting, and one must be innocent.