Following the Battle of New York, Adrian Toomes and his salvage company are contracted to clean up the city, but their operation is taken over by Tony Stark’s U.S. Department of Damage Control (D.O.D.C.). Enraged at being driven out of business, Toomes persuades his employees to keep the Chitauri technology they have already scavenged and use it to create and sell advanced weapons. Eight years later, Peter Parker is drafted into the Avengers by Stark to help with an internal dispute, but resumes his studies at the Midtown School of Science and Technology when Stark tells him he is not yet ready to become a full Avenger.
Parker quits his school’s academic decathlon team to spend more time focusing on his crime-fighting activities as Spider-Man. One night, after preventing criminals from robbing an ATM with their advanced weapons from Toomes, Parker returns to his Queens apartment where his best friend Ned discovers his secret identity. On another night, Parker comes across Toomes’ associates Jackson Brice / Shocker and Herman Schultz selling weapons to local criminal Aaron Davis. Parker nearly drowns intervening, and is rescued by Stark, who is monitoring the Spider-Man suit he gave Parker and warns him against involvement with the dangerous criminals. Toomes accidentally kills Brice with one of their weapons, and Schultz becomes the new Shocker.
Parker and Ned study a weapon left behind by Brice, removing its power core. When a tracking device on Schultz leads to Maryland, Parker rejoins the decathlon team and accompanies them to Washington, D.C. for their national tournament. Ned and Parker disable the tracker Stark implanted in the Spider-Man suit, and unlock its advanced features. Parker tries to stop Toomes from stealing weapons from a D.O.D.C. truck, but is overpowered and trapped inside the truck, causing him to miss the decathlon tournament. When he discovers that the power core is an unstable Chitauri grenade, Parker races to the Washington Monument where the core explodes and traps Ned and their friends in an elevator. Evading local authorities, Parker saves his friends, including his fellow classmate and crush Liz. Returning to New York City, Parker persuades Davis to reveal Toomes’ whereabouts. Aboard the Staten Island Ferry, Parker captures Toomes’ new buyer Mac Gargan, but Toomes escapes and a malfunctioning weapon tears the ferry in half. Stark helps Parker save the passengers before admonishing him for his recklessness and taking away his suit.