When the fabled Star of Rhodesia diamond is stolen on a London to Edinburgh train and the son of its owner is murdered, Sherlock Holmes must discover which of his suspicious fellow passengers is responsible.

A herpetologist investigating a series of fatal rattlesnake attacks discovers that the creatures have been infected by a mysterious nerve gas disposed of in the desert by the military.

Two hoodlums, brothers, are shot and wounded during an attempted robbery. They are taken to a nearby hospital where they learn that their actions can have serious consequences.