In Amazing Spider-Man #510, Peter receives a letter from his assailants in which they threaten to kill Mary Jane and Aunt May. Not wanting to alarm them, Peter remains silent about the content of the letter. Later, as Spider-Man, Peter pays a visit to Detective Lamont to get help in obtaining some latent handwriting impressions from Gwen's letter. After leaving Lamont, he calls his aunt to check on her. A male voice answers the phone and tells him that he has to make his way to a certain address in less than ten minutes or else Aunt May dies. Peter/Spider-Man web-slings as fast as he can and reaches the destination. As he approaches what appears to be Aunt May tied to a chair in the middle of the factory, his spider-sense goes ballistic and he realizes that it is a trap. He escapes a huge explosion that completely destroys the factory but he is partially caught in the blast. As he lies in the rubble of the factory, bruised and battered, the male assailant shows up and starts beating him to a bloody pulp. The intervention of the female assailant saves his life. The male assailant, however, vows to return and finish what he has started. Their names are revealed - the woman is named Sarah, the man Gabriel. Later that night, Peter/Spider-Man meets once again with Detective Lamont. The letter reveals that Gwen was pregnant when she left for Europe and that she had twins - their names: Gabriel and Sarah.

In Amazing Spider-Man #511, a distraught Peter tries to make sense of this shocking revelation. The scientist in him knows that it is impossible for Gabriel and Sarah to be Gwen's kids because if it were true, they would be children, not full-grown adult, such is the case here. As Spider-Man, he heads over to a Genetic Lab to perform some DNA testing using DNA left on the letter (by either Gabriel or Sarah) and DNA extracted from Gwen's grave during an earlier visit to the cemetery. While there, he is confronted, at gunpoint, by Sarah, who tells him that Gabriel doesn't want to just kill him but to make him suffer by killing everyone he loves. Sarah appears to hesitate when Peter asks her if she wants the same thing as her brother but she replies that the only way Peter can save the people he cares about is to willingly let her kill him right there, right now. Peter is literally saved by the bell of the DNA testing machine, which catches Sarah off-guard. Peter uses that opportunity to lunge himself at her and disarm her. He then pulls her mask off and is shocked to see that she looks exactly like her mother, Gwen Stacy. At that moment – almost on cue – a nearby window blows up, courtesy of a very impatient Gabriel, who had been waiting outside on a nearby rooftop. While Peter dives out of harm's way, Sarah storms out of the building and reunites with her brother, who immediately jumps to the conclusion that Peter's presence at the genetic lab confirms that he is their father and that he deserted their mother and later caused her death. Back in the lab, Peter checks on the DNA results, which confirm that Sarah and Gabriel are indeed the children of Gwen Stacy. Later, when Peter returns to his apartment, he finds a very distressed Mary Jane waiting for him. MJ tells him that she found the letter and read it. Peter replies that it can't be his kids because Gwen and him never slept together. MJ believes that Peter is telling the truth because she knows who the real father of Gwen Stacy's children is.

In Amazing Spider-Man #512, Mary Jane reveals to Peter that Norman Osborn is the father of Gwen’s children. It is also revealed that the twins are aging prematurely, as a result of the goblin formula coursing through their bloodstream, which they genetically inherited from their father. More information is introduced to tie some of the loose ends and plots holes of this farfetched story. For instance, the Green Goblin, Norman's alter ego, not only killed Gwen (on the Brooklyn Bridge back in Amazing Spider-Man #121) because she was Peter’s girlfriend but he killed her because she did not want him around her children; even though they were his as much as they were hers. As well, Peter realizes that the reason Osborn was after him to become his heir back in Amazing Spider-Man #25 (466) and Peter Parker Spider-Man #25 (123) was that he had brainwashed his kids into thinking that Peter was their father, therefore he was trying to coerce Peter into becoming part of his family so that he would take his rightful place as their father. Of course, that didn't work so Norman kept quiet about them. He did however continue to brainwash them into thinking that Peter had abandoned their mother and later caused her death, which is why they are so mad at Peter now. At issue's end, Peter realizes that he must try and save them because at the rate they are aging, they might die in a few years.

In Amazing Spider-Man #513, Peter, as Spider-Man meets Gabriel and Sarah atop the Brooklyn Bridge to try and talk to them. He explains everything that he knows and he tells them that Norman Osborn is their father and that this whole thing is another one of his twisted evil scheme. Sarah believes him since Peter never slept with Gwen but Gabriel doesn’t. He attacks Peter but Peter doesn’t want to fight him. In the midst of the battle, Gabriel fires a gunshot, which strikes his sister Sarah when Peter jumps out of harm’s way. Sarah falls off the bridge and begins falling to her death. Peter, however, comes to her rescue and saves her from imminent death, while Gabriel flees the scene. Peter brings Sarah to the hospital to get immediate medical attention. Meanwhile, Gabriel makes his way through the sewer system to a location he somehow remembers being told about by Norman Osborn. He enters some kind of underground facility and comes face to face with two large containment units containing two Green Goblin costumes, a green and purple one intended for Sarah and a blue and grey one intended for him. This is where this issue picks up.

ACT 1: Gabriel drops down to his knees and just can't believe it, repeating: "it can't be…it can’t be". At that moment, his voice activates some kind of voice-recognition system and Norman Osborn's face appears on a nearby TV screen. The Norman on the screen explains how he wants Gabriel and Sarah to take over the mantle of the Green Goblin and follow in his footsteps. Gabriel is shocked and cannot believe what he is seeing, that Norman lied to him and Sarah all these years about Peter/Spider-Man, about their mother, about him being their father.

ACT 2: Meanwhile, at the hospital, Peter/Spider-Man is waiting outside the door to Sarah's room. He is soon joined by Mary Jane who tries to comfort him. After a few hours, a surgeon comes out of the room and informs them that the surgery worked and that the bullet was extracted from the wound. However, he tells them that they are having a hard time finding a match for her blood and that every time they tried a perfect match, her body rejected it (Peter realizes that Norman's blood is what's causing her body to reject any other blood). The doctor goes on explaining that they've been transfusing synthetic plasma into her bloodstream for now but that it will only last for so much time. The doctor asks Spidey if he is aware of any next of kin to which Spidey replies that she does have some but that they wouldn't be able to make it there on time. The doctor retorts that they'll do their best to keep her comfortable as long as possible...until the end. Peter/Spider-Man doesn't want to lose Sarah so he makes the drastic decision of having HIS blood transfused into HER body.

ACT 3: Back at the secret hideout, the Norman on the screen explains that he possesses a serum that will slowly deactivate Gabriel's advanced aging and make him very powerful, although there might be some secondary effects on his mental processing, disruptions in normal functioning, paranoia, psychosis and even some memory loss. At that moment, a small device holding two syringes comes out of the floor. Hesitating at first, Gabriel takes one of the syringes and shoots its content into his arm. At that exact moment back at the hospital, Sarah slowly emerges from her coma thanks to the blood transfusion from Peter/Spider-Man.

ACT 4: A short while later, Peter/Spider-Man recuperates from the blood transfusion in a separate area of the hospital and Mary Jane is by his side. MJ tells him that the press is all over the place downstairs but that the hospital is trying to keep everything quiet. At first, Peter doesn't react to what she just said but after pondering about it for a minute, he realizes that if the press has gotten wind of his presence there, Gabriel probably did as well. On cue, Gabriel, dressed in the blue and grey Goblin costume, shows up and grabs Peter/Spider-Man right out of his hospital bed, just as he did with Sarah; revealed on the next page. Gabriel brings Peter/Spider-Man on the rooftops and the two foes battle it out, although Spidey is very groggy from the recent blood transfusion. In the midst of all this, Sarah, who's been dragged to the rooftops as well, shows up with a gun and points it at her brother and tells him to get away from Peter/Spider-Man and her. Gabriel struggles with the idea of having to fight his own sister for a mere few seconds but the Goblin formula coursing through his veins is too powerful and he launches a bunch of missiles at his sister. Sarah leaps out of harm's way and unloads her gun at him. Two bullets hit the goblin glider, sending it out of control, and the glider finally blows up, sending Gabriel to his apparent death in the Hudson River.

ACT 5: Back on the rooftops, Sarah drops her gun and starts to walk away from Peter/Spider-Man who is lying on the ground barely conscious. Peter/Spider-Man implores her to stay but he passes out as she makes her way down the stairs. He awakens a few minutes later, with Mary Jane looking over him, telling him to go to sleep.

ACT 6: Elsewhere, the body of Gabriel washes up on a beach and is found by some vacationers. He is still alive but heavily bruised and battered. When the man who found him asks his name, Gabriel doesn't remember. The End.