Travis Bickle is a lonely and depressed young man a living in Manhattan - he suffers from heavy depression living most of his life alone. He becomes a night time taxi driver in order to cope with his chronic insomnia, working 12-hour shifts nearly every night, carrying passengers around all five boroughs of New York City. His restless days, meanwhile, are spent in seedy porn theaters. He keeps a diary (excerpts from which are occasionally narrated via voice-over during the film). Bickle is an honorably discharged Marine, and it is implied but never mentioned in the screenplay that he is a Vietnam veteran; he keeps a charred Viet Cong flag in his squalid apartment and has a large scar on his back.