After saving a friend of Aunt May's Ernie Popchik from three muggers, Spider-Man is informed by some cops who support him that his good friend and ally Jean DeWolff was murdered in her sleep last night. He is shocked by the news and goes to Jean's precinct to offer his assistance in solving the murder. Stan Carter, the detective who was investigating the case tells him that Jean's badge was missing and it was most likely taken by the killer. Stan also told Spidey that Jean's admiration for him may have been more than professional and Peter admits that he liked her too.
Later on, Matt Murdock (Daredevil) is legally defending the same muggers that attacked Popchik in an arraignment trial and he successfully has them released on bail. Peter, who was at the hearing, expresses his disgust of Matt's actions and the lawyer instantly recognizes him as Spider-Man by his distinctive heartbeat. After the hearing, Matt confides in the presiding judge who is also his friend and mentor and tells him that despite his belief in equality under the law, he shares Peter's perspective on the whole situation but the judge tells him that he doesn't like working with guilty people and he seems indifferent on the situation. A masked man holding a shotgun, referring himself as the Sin-Eater, then enters the room and Matt attempts to fight him but fears compromising his secret identity as Daredevil so he ends up freezing in place and the villain kills the pleading judge with his shotgun. The gatherers at the courthouse flee after hearing the gunshot, and as Eater escapes through a window, Matt changes into Daredevil and goes to capture him. Meanwhile, Peter, who has also heard the gunshot, changes into Spider-Man and goes to fight Eater. Outside the courthouse, Spider-Man confronts the murderer who quickly opens fire on him and although Spider-Man dodges the shot, it hits and injures one of the gathering civilians instead. Spider-Man is overcome with guilt over unintentionally injuring a civilian, causing Peter to be defeated by the Eater, who is a formidable opponent. He then notices a police badge on Eater's belt and deduces that he was in fact Jean's killer and when accused, Eater admits of his crimes. And while the Eater is explaining about his mission, Spider-Man manages to punch him a few feet away. Spidey sees Aunt May lying on the ground and the Eater manages to escape because Spidey's web-shooters were damaged during the fight. Spider-Man becomes more determined than ever to capture this new villain.
Spider-Man then visits Carter in his office and informs him that the Eater is Jean's killer. Carter tells Spidey that the criminal's name refers to a superstitious belief about the absorption of the wrongs of other by killing people for their transgressions and taking symbolic token from the victims. Spider-Man then goes to Jean's apartment to search for some clues that might have been missed by the police. Although he doesn't find any, he comes upon a photograph of him and Jean, and he realizes that Jean was in fact in love with him, causing her death to become even more painful for him. During DeWolff's funeral, Matt was able to sense the Eater's presence using his enhanced senses but was unable to do anything about it because of the large gathering at the funeral. Later in the day, Eater kills the priest who oversaw the funeral of DeWolff. Spider-Man then goes on a rampage in the criminal underworld and attempts to force some low-level thugs into giving him information about the murderer but he receives nothing.
At the Daily Bugle, Eater appears looking for J. Jonah Jameson and before he could kill Joe Robertson, Peter Parker, who was at the Bugle, knocks him out using the roller of a typewriter. The Eater is unmasked and taken by the police. During the interrogation which is being attended by Daredevil and Spider-Man, the suspect is identified as Emile Gregg who tells his interrogators that he was hearing voices the prompted him to commit the crimes. However, Daredevil, hearing Gregg's heartbeats realizes that Gregg is lying and tells Spider-Man that he may have not committed these crimes and convinces him to search Gregg's apartment. They discover that Gregg's apartment is adjacent to Carter's which contains several Eater costumes and guns. Daredevil deduces that Carter is the real murderer and Gregg, who was obviously mentally unstable, heard Carter recording his own thoughts using a tape recorder they found and thought they were voices in his head. The heroes recall that Eater intended to kill Jameson and is most likely going to Jonah's penthouse where Betty Brant and Marla Jameson are while Jonah is attending a conference in Florida. Indeed, Eater goes to Jonah's penthouse and when he was about to kill Betty, Spider-Man crashes through the window just in time and viciously pummels Eater while Betty watches in horror. Daredevil appears and prevents an enraged Spider-Man from killing the unconscious Carter. However, in his current state of mind, Spider-Man punches Daredevil out of the apartment. Daredevil regains his footing and starts taunting Spider-Man who is easily provoked in his current mindset and goes to fight Daredevil but the Man Without Fear manages manages to defeat Spider-Man who's fighting abilities are diminished by his rage by confusing his spider-sense and beating him to unconsciousness with his billy club.
Carter is taken into custody and it is revealed that he was driven insane by drugs after his partner was killed. When it is revealed that Carter may be found innocent by insanity, a group of angry civilians, including Jean's father, who were willing to punish Carter for his crimes assaulted the precinct looking for Carter. Daredevil tried to save Carter but he was overwhelmed by the mob and he asked for help from Spider-Man who turned his back and walked away because he though Carter deserved what was about to happen to him. In a desperate attempt to save himself and Carter, Daredevil cried out Spider-Man's real name causing Peter to instinctively swing by and save both Daredevil and Carter. On a rooftop, both Spider-Man and Daredevil reveal each other's secret identities to each other and Matt even offered his legal services to Peter if he needed. This solidified the friendship between the superheroes.