Full story
Two years into being Spider-Man, Peter Parker is going under. He loses his pizza delivery job, falls behind in college, can't make rent and Aunt May may lose her house. Mary Jane is a hit on the stage and is engaged to John Jameson, an astronaut and the son of the Daily Bugle's owner. Harry Osborn, now running Oscorp's science division, still hates Spider-Man for his father's death.
Harry funds the work of Otto Octavius, a scientist Peter admires: a fusion reactor powered by tritium. To control it, Otto uses four mechanical arms with their own intelligence, attached to his spine by a chip that protects his mind. At the demonstration, the reactor goes haywire, his wife Rosie is killed and the chip burns out. The arms are fused to his body and start whispering in his head. The Bugle dubs him Doctor Octopus.
Otto decides to rebuild the experiment and robs a bank to fund it, with Peter and Aunt May inside. He takes May hostage, and Spider-Man saves her. Meanwhile, Peter starts losing his powers: his webs fail and he falls off buildings. A doctor suggests the problem is Peter himself. He throws the suit in the trash and tries to live a normal life. His grades go up and he gets closer to Mary Jane. But crime in the city rises. Peter tells Aunt May he had a part in Uncle Ben's death, and after the shock, she forgives him and talks about what heroes mean to people.
Otto needs more tritium, and Harry agrees to supply it if Otto brings him Spider-Man. Otto kidnaps Mary Jane from a café. Desperate to save her, Peter focuses and his powers come back. He fights Doc Ock on a runaway train and stops it with his own body, unmasked, until he passes out. The passengers carry him and promise to keep his secret. Doc Ock delivers him to Harry, who pulls off the mask and finds his best friend.
Peter talks Harry into telling him where Otto is and heads to the reactor on the waterfront. He shows Otto his face and convinces him to stop. Otto takes back control of the arms and sinks the reactor in the river, dying with it. Mary Jane sees Peter without the mask and understands everything. Harry sees a vision of his father in a mirror and finds the Green Goblin's hideout, a thread that comes back later. On her wedding day, Mary Jane leaves her fiancé and runs to Peter. When they hear sirens, she tells him to go.