Isolated ex-marine Travis Bickle applies for a job as a taxi driver, hoping that the nocturnal working pattern will alleviate the effects of his insomnia and distract him from his gnawing depression. But ferrying passengers through the seedy underbelly of night-time New York City only compounds Bickle's psychological dislocation from the world around him. His nightshifts in the cab are spent resenting those he sees, while his waking daytime hours are wasted away in adult movie theatres.
After entering into a troubled relationship with a political campaigner and embarking on a fraught mission to save a teenager from the world of prostitution, Bickle's sense of place and purpose steadily warps. He withdraws into himself, hordes illegal firearms and begins a regimen of intense physical training in preparation for a misguided vigilante assault on the evils of society.