A runaway train, transporting deadly, toxic chemicals, is barreling down on Stanton, Pennsylvania, and proves to be unstoppable until a veteran engineer and young conductor risk their lives to try and stop it with a switch engine.

A chronicle of the original Mercury astronauts in the formation of America's space program: Alan Shepherd, the first American in space; Gus Grissom, the benighted astronaut for whom nothing works out as planned; John Glenn, the straight-arrow 'boy scout' of the bunch who was the first American to orbit the earth; and the remaining pilots: Deke Slayton, Scott Carpenter and Wally Schirra.