Amazing Spider-Man (Vol. 1) #135

Story 'Shoot-Out in Central Park!'

Darting home during a brief respite from his difficult day slugging it out with the Punisher and the Tarantula, Peter Parker tosses his Spider-Man costume in an open drawer on his way to a shower. This is a piece of carelessness that will cost him dearly. His stressed-out room-mate, Harry Osborn, finds the costume. This confirms his long held suspicion that Peter Parker is Spider-Man, whom he holds responsible for the death of his father, Norman Osborn, also known as -- the Green Goblin!

As Spider-Man and the Punisher reluctantly team-up to trap the Tarantula, Harry Osborn makes his way to a deserted warehouse. "This is where he killed my father... What I need...I'll find here." A secret door opens. Harry walks in. The door slams shut behind him.