Taxi Driver (1976)

Suffering from insomnia, disturbed loner Travis Bickle (Robert De Niro) takes a job as a New York City cabbie, haunting the streets nightly, growing increasingly detached from reality as he dreams of cleaning up the filthy city. When Travis meets pretty campaign worker Betsy (Cybill Shepherd), he becomes obsessed with the idea of saving the world, first plotting to assassinate a presidential candidate, then directing his attentions toward rescuing 12-year-old prostitute Iris (Jodie Foster).