Travis develops hatred toward those who have spurned him, including Betsy, the New York senator for whom Betsy campaigns, and Sport, Iris' pimp. Travis' mounting anger is conveyed through a series of scenes in which he transforms his physique into the sculpted frame of a hired killer; he performs countless exercises, including sit-ups, pull ups, and weight lifting. He engages in target practice in order to improve his marksmanship, and perfects his gun-drawing technique as well. If the scenes with Travis in his taxi cab represented the initial stage of the Campbellian mythical trajectory, in which the hero becomes aware of their surroundings and the need for a better life, the scenes in which Travis purchases guns and exercises exemplify the second stage of the process, albeit in a somewhat unusual manner. Where the second stage of the journey involves the hero undergoing a series of tests in which they acquire knowledge and experience, in Taxi Driver such tasks are not imposed upon Travis from without but instead are devised by him. Indeed, no one tells him to put himself through innumerable exercises or become a skilled marksman; instead, Travis' actions are in response to an external reality that necessitates improvement. In addition to his physical training, the other aspect of Travis' initiation process (stage two of the Campbellian mythical structure) involves his rescuing of Iris. One day, he spots Iris on the street and then becomes motivated to help save her. He then pays for her services, but instead of having sexual intercourse with her, he attempts to convince her to leave her profession. However, Iris does not work as a prostitute out of necessity and actually enjoys her work. A subsequent scene involves Travis taking Iris out to breakfast (a parallel with the earlier scene in which he has coffee and pie with Betsy) but again she insists that she will remain committed to remaining as a prostitute.

Through the initiation process, Travis becomes an active hero. He transitions from an observer of criminal activity (while driving the city streets) to actively working toward combating what he sees as immoral. He then continues the second stage of the Campbellian journey only in a more active way, in preparation for the third stage, which involves the hero returning to their original state, endowed with the knowledge gained from stage two. Admittedly, Travis does not physically return to his initial state since he never leaves the New York cityscape, more forcefully attempting to provide assistance in helping Iris. He shaves his head...

Following his arrival, he is stopped by Sport but then shoots both him and then a bodyguard in the house of prostitution. Sport is able to recover but Travis kills him. Travis then attempts to kill himself, although his gun is out of bullets and instead, he is taken by the police and placed into a hospital for recovery. While recuperating, he receives a missive from Iris' family stating that Iris has decided to quit her job as a prostitute and she has reinhabited her role as faithful daughter. The film concludes with Travis returning to his profession as a taxi driver, a return to the position in which the film began.
Taxi Driver is an interesting example of the Campbellian mythical trajectory because it must balance the hero's three step journey while at the same time remaining faithful to the precepts of classical narration. The course of Travis' journey does not involve any romantic involvement and in this regard the film deviates from classical narration; instead, his romantic interest is replaced by a devotion to guns that sublimates any erotic desire. Ultimately, Travis uses his knowledge of guns place his life in danger and kill Iris' pimp, allowing her to return to her quiet family life. Although the film is often dark and despairing, Travis' ultimate victory in rescuing Iris assimilates the film within the Campbellian mythical framework.