A clever fortune-hunter with a penchant for murder does in his elderly, supposedly rich, wife and manages to get away with it. After an investigation results in a decision of 'accidental death'...

正要赶往伦敦完婚的凯莉（MargaretLockwood）因雪崩被困在山下的小旅馆里，偶遇摄影记者康德（MichaelRedgrave），两个人因小事发生争执，第二天大家各自赶路，却登上了同一列火车。\r在车上凯莉与一名老妇人佛洛伊（DameMayWhitty）结伴，彼此照料。然而凯莉因头部被撞，恍惚中沉沉睡去，待她醒来，老妇人不见了。四处寻找佛洛伊，却不见她的踪影，凯莉只好报警。出乎意料的是同车...