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.
After a police chase with an otherworldly being, a New York City cop is recruited as an agent in a top-secret organization established to monitor and police alien activity on Earth: the Men in Black. Agent Kay and new recruit Agent Jay find themselves in the middle of a deadly plot by an intergalactic terrorist who has arrived on Earth to assassinate two ambassadors from opposing galaxies.