Kimble is blackmailed into slaving for a physician obsessed with curing a deadly strain of meningitis prevalent in a remote Mexican province. The fugitive put ashore in Mexico, after fleeing U.S. police, and swapping places with a departing sailor. The expatriate Dr. Howell will stop at nothing to wipe out his "tiny enemy," but Richard Kimble contests the ethics of Howell's fanatical methods, as a wily local police sergeant closes in on the convicted killer.