High-school senior Peter Parker lives with his Aunt May and Uncle Ben, and is a school outcast. On a school field trip, he visits a genetics laboratory with his friend Harry Osborn and love interest Mary Jane Watson. There, Peter is bitten by a genetically engineered “super spider.” Shortly after arriving home, he becomes unconscious. Meanwhile, Harry’s father, scientist Norman Osborn, owner of Oscorp, is trying to secure an important military contract. He experiments on himself with an unstable performance-enhancing chemical. After absorbing the chemical, he goes insane and kills his assistant.
The next morning, Peter finds that he is no longer near-sighted, and his body has metamorphosized into a more muscular physique. At school, he finds that his body can produce webs, and his quickened reflexes let him avoid injury during a confrontation with Flash Thompson. Peter discovers he has developed superhuman speed, strength, the ability to stick to surfaces, and a heightened ability to sense danger.
Brushing off Ben’s advice that “with great power comes great responsibility,” Peter thinks of impressing Mary Jane with a car. He enters an underground fighting tournament and wins his first match, but the promoter cheats him out of his money. When a thief suddenly raids the promoter’s office, Peter allows him to escape. Moments later, he discovers that Ben was carjacked, and killed. Peter pursues and confronts the carjacker, only to realize it was the thief he let escape. After Peter disarms him, the carjacker flees but dies in the process. Meanwhile, a crazed Norman interrupts a military experiment by Oscorp’s corporate rival and kills several scientists and the military’s General Slocum.
Upon graduating, Peter begins using his abilities to fight injustice, donning a costume and the persona of Spider-Man. J. Jonah Jameson, a newspaper company headmaster hires Peter as a freelance photographer since he is the only person providing clear images of Spider-Man.