Spidey returns from Infinity War with the new suit when he catches some muggers or whatevs. He hands them over to Jean DeWolff, and we learn through some banter that they're friendly. Jean is one of only a few members of the police force who aren't giving Spidey, Daredevil, and other vigilantes a hard time. She, like Spidey, is having an awful time dealing with JJJ. Jean mentions that while Spidey's been off in space, she's been tracking a serial killer named Cletus Kassady who also goes by the name of Sin Eater. (This is a slight variation on the comics.)
Jean is killed by Sin Eater. Spidey teams up with Daredevil to hunt him down. They finally get a hold of Sin Eater. The black costume has now altered Spidey's behavior to the point where he's unable to control himself, beating Sin Eater nearly to death. Daredevil intervenes, they fight. Daredevil notices the costume seems to have the same sensitivity to sound that he does. He ends the fight by telling Spidey he knows his identity, and the two of them head over to Avengers Tower where RDJ, earning $15 million for 15 minutes worth of work, blasts the costume off with a doohickey. The costume slinks off. In the post credits scene we see the costume find Eddie Brock who got introduced as Peter's rival earlier in the movie.
