The final installment of the Back to the Future trilogy finds Marty digging the trusty DeLorean out of a mineshaft and looking for Doc in the Wild West of 1885. But when their time machine breaks down, the travelers are stranded in a land of spurs. More problems arise when Doc falls for pretty schoolteacher Clara Clayton, and Marty tangles with Buford Tannen.
Members of an American scientific research outpost in Antarctica find themselves battling a parasitic alien organism capable of perfectly imitating its victims. They soon discover that this task will be harder than they thought, as they don't know which members of the team have already been assimilated and their paranoia threatens to tear them apart.
A boy with a massive facial skull deformity and biker gang mother attempts to live as normal a life as possible under the circumstances.
When a dispute occurs between a logging operation and a nearby Native American tribe, Dr. Robert Verne and his wife, Maggie, are sent in to mediate. Chief John Hawks insists the loggers are poisoning the water supply, and, though company man Isley denies it, the Vernes can't ignore the strangely mutated wildlife roaming the woods. Robert captures a bear cub for testing and soon finds himself the target of an angry mutant grizzly.
Hungarian physicist Leo Szilard leaves Europe, eventually arriving in the United States. With the help of Einstein, he persuades the government to build an atomic bomb. The project is given to no-nonsense Gen. Leslie Groves who selects physicist J. Robert Oppenheimer to head the Los Alamos Laboratory in New Mexico, where the bomb is built. As World War II draws to a close, Szilard has second thoughts about atomic weapons, and policy makers debate how and when to use the bomb.
An armored car driver tries to elude a gang of thieves while a flood ravages the countryside.