Peter Parker plans to propose to Mary Jane Watson, who has just made her Broadway musical debut. Meanwhile, a small meteorite crashes near the two in Central Park, and an extraterrestrial symbiote attaches itself to Peter's moped. Elsewhere, police pursue escaped prisoner Flint Marko. He climbs a security fence and falls into an experimental particle accelerator, which fuses his body with the surrounding sand and allows him to shapeshift at will as the Sandman.
Peter's ex-best friend, Harry Osborn, who knows Peter is Spider-Man and believes that Peter is responsible for his father Norman Osborn's death, attacks Peter using new weapons based on his father's Green Goblin technology. Harry injures his head on a pipe and suffers from partial amnesia, making him forget his revenge and that Peter is Spider-Man.