老夫婦於火車上被殺，乘客頓成疑犯。大偵探抽絲剝繭，卻無法找出兇手。難道真兇在火車高速行駛下逃去無蹤？

When an elderly couple is found murdered aboard a speeding train, every passenger becomes a suspect. Sherlock Holmes is baffled by the case. How could the killer vanish without a trace on a train hurtling at high speed?