Full story
When Peter Parker is a boy, someone ransacks his father Richard's office. Frightened, Richard and Mary leave him with his aunt and uncle, May and Ben, and disappear. Years later, Peter is a shy, brilliant student at Midtown Science High, quietly crushing on classmate Gwen Stacy. In the basement he finds his father's old briefcase and learns that Richard worked at Oscorp with Dr. Curt Connors on research that mixed DNA from different species.
Peter sneaks into Oscorp and introduces himself to Connors, a scientist missing his right arm who dreams of regrowing limbs the way lizards do. In a restricted room, a modified spider bites Peter. The next day he is stronger, faster and sticks to walls. Peter gives Connors the missing formula, hidden in his father's notes.
At home, Peter has a big fight with Uncle Ben and storms out. Ben goes looking for him and gets shot by a thief Peter had let get away minutes earlier. Driven by guilt and anger, Peter starts hunting criminals who match the killer's description. He makes the mask, the suit and mechanical web-shooters, and becomes Spider-Man. At dinner with the Stacys, he finds out Gwen's father is Captain George Stacy, who treats the masked hero like a criminal. Peter tells Gwen the truth, and they get together.
Pushed by Oscorp, which wants human trials, Connors tests the serum on himself. His arm grows back, but he turns into the Lizard, a giant creature that causes a disaster on the Williamsburg Bridge. Spider-Man saves people, including a boy trapped in a car. Connors figures out who Peter is and attacks him at school. In the sewers, Peter discovers the plan: release a chemical cloud from the top of Oscorp Tower to turn all of New York into lizards.
The police corner Peter and Captain Stacy sees his face, but lets him go. Gwen mixes the antidote at Oscorp. At the top of the tower, the captain fights the Lizard while Peter swaps the cloud for the antidote, curing Connors and everyone affected. Mortally wounded, Captain Stacy asks Peter to stay away from Gwen to keep her safe. Peter tries, but in the last scene he hints to Gwen that he won't manage it. After the credits, a mysterious man visits Connors in prison and asks if Peter knows the truth about his father. Connors says no. That comes back later.