In Los Angeles, humans live alongside extraterrestrial humanoid beings whose spaceship crash landed three years earlier. This coexistence is not always harmonious, as exemplified by segregated slums and the uneasy partnership of police detective Matthew Sykes (James Caan) with new humanoid partner Sam Francisco (Mandy Patinkin). However, the pair begin to overcome their differences as they investigate a slum drug ring led by the slippery William Harcourt (Terence Stamp).