Mary Jane, thinking that Peter might be at the Daily Bugle, stops by and runs into John Jameson, who gives her a weird vibe. She pretends to have to go and takes off. As she leaves, she unknowingly drops her scarf, which is picked up by John.

Peter, as Spider-Man, is out on patrol when he gets a disturbing phone call from Dr. Connors, who appears to be on the verge of transforming into the Lizard. Spidey swings towards Connor's apartment but arrives a few seconds too late, as both Connors and his son, Billy, are transformed into lizards.

In Sensational Spider-Man #24, Spider-Man confronts the two lizards and, during the ensuing battle, gets hurt quite severely. He flees to the rooftop, the lizards in tow, where he runs into the Black Cat. As if suddenly possessed by a wild animal, the Black Cat savagely attacks the Doctor-Lizard while the Billy-Lizard attacks Spidey. The Black Cat fares well and sends her opponent off the rooftop. Spidey has a rather difficult time with the Billy-Lizard; however, he gets unexpected (and unwanted) help when a nosy neighbor armed with a rifle shoots the Billy-Lizard. At issue's end, the Billy-lizard has transformed back into his human self and he is bleeding to death from his gunshot wound.

While all this takes place, Mary Jane gets an unexpected visit from John Jameson, who is bringing back the scarf she accidentally dropped at the Daily Bugle in the previous issue. MJ feels uneasy about letting him in Avengers Tower but Aunt May invites him in for tea and biscuits. On his way in, John attacks the doorman in the lobby for drinking on the job. He then makes his way up.

This issue also marks the long-awaited return of Vermin who unwillingly comes to the aid of a prostitute by killing her crooked cop-pimp and feeding on his flesh.

In Sensational Spider-Man #25, Spider-Man, accompanied by the Black Cat, takes Billy Connors to the Fantastic Four Headquarters to get help from Susan and Reed Richards. Billy is immediately put inside some kind of bio-bath and while he recuperates, Reed performs tests on both Spidey and the Black Cat to determine why they, like so many others, have been experiencing bouts of extreme anger.

Meanwhile, at Avengers Tower, John Jameson transforms into the Man-Wolf and attacks Mary Jane and Aunt May. Thankfully, they manage to lock themselves in the kitchen and activate the defense system. Several blocks away, Spidey senses that MJ and Aunt May are in danger and rushes back to their rescue, leaving the Black Cat to be further probed. When he arrives at the tower, MJ and Aunt May have already been saved by a herd of Iron Men who were alerted by the distress signal sent out when the defense system was activated. Peter/Spidey is left wondering what just happened.

Somewhere in the New York City sewers, the Lizard, recovering from his skirmish with the Black Cat, is tormented by memories of injecting his own son with a bio-restorative serum, as "told" by the meteor rock he was called on to study in Sensational Spider-Man #23. He lets out a roar that echoes through the sewers and reaches the ears of Vermin, who is feasting on the crooked cop-pimp he murdered in last issue. Vermin lets go of his victim and takes off towards the Natural History Museum. The Lizard takes off in the same direction. Meanwhile, back at the Fantastic Four Headquarters, the Black Cat takes off through a window, having had enough of being poked and probed.

At issue's end, Peter, as Spider-Man, takes off into the night and goes to meet the one person that can provide him with some extrasensory help: Madame Web.

In Sensational Spider-Man #26, Madame Web doesn't really help him that much, except that she makes the suggestion that he should chase the Lizard to the source of the "infection": Central Park. While Spider-Man heads over there, the Black Cat runs into the Puma who is also somewhat under the spell of whatever is making everybody angry. They have a brief tussle instigated by Puma but it is exactly what she needed to relieve some of her built-up anger (Puma actually convinced her to fight him because he knew that it would help her calm down and satisfy her hunger).

Meanwhile, at the Fantastic Four headquarters, Mister Fantastic, who has been conducting experiments on the recently captured John Jameson, reaches the conclusion that something radioactive is at the source of the "infection". While this discovery is made, Puma and the Black Cat make their way towards Central Park, where they are being drawn.

The Lizard is making his way through Central Park when he is attacked by Vermin. The two of them battle it out for a while until Spider-Man shows up and jumps in the mêlée. The fight spreads out into a nearby lake where Spidey manages to momentarily get rid of his adversaries. But as he climbs ashore, he comes face-to-face with what appears to be the source of the "infection" and the mastermind behind it: Dr. Vincent Stegron, a half-man half reptile.

This is where this issue picks up.

ACT 1: The issue starts with Dr. Vincent Stegron, in his human form, making his way to the Artic Circle where he makes the amazing discovery of the rock of life. The rock of life is said to be the prime asteroid, from which life first sprang and whose physical properties changed overtime, eventually triggering the great ice age. The rock of life also gives off a radiation that disrupts the very laws of nature and science, thus reversing the evolutionary process. Stegron took said rock and brought it back to New York City. During the trip back however, he soon discovered that the rock could grant him his greatest wish: bringing the thunder lizards back to life. As such, he began to devolve and transformed more and more into his reptile self as the voyage progressed. Upon his return in New York City, Stegron shipped the asteroid to a friend of his, Dr. Treyman, from the Museum of Natural History, who in turned called upon Dr. Curt Connors, seeking his assistance. From there on, Stegron waited as the radiation started to seep across the City, causing things to change and devolve, until the time came for him to claim back his kingdom.

ACT 2: Spider-Man punches Stegron and sends him flying through a wall and into the Museum of Natural History, which is near Central Park. Stegron retaliates with a few punches and even has some of his reptiles, most notably raptors, join him in his fight against Spidey.

ACT 3: Vermin and the Lizard are still battling out and are starting to slow down, fatigue creeping on them. Puma and the Black Cat, who are watching the fight from up in a tree, decide to make their move against the two miscreants. Within mere seconds, Puma and Vermin are neutralized.

ACT 4: Inside the museum, Spidey encounters a human, presumably a museum worker, who appears to have devolved back into a caveman and who attacks him. Not wanting to hurt him, Spidey uses his appendages to pin the man against a wall and web him up. Stegron uses this moment of distraction to slam his giant tail into Spidey, who is thrown to the floor. Stegron proceeds to try and crush him with his two feet but Spidey leaps out of harm's way. As he flees from Stegron, Spidey gets a call (via his costume) from Reed Richards, onboard the Fantastic Four quinjet, who informs him that Stegron is a symptom of the problem. Spidey couldn't agree more, as Stegron's tail comes crashing into the wall behind him. Reed tells Spidey to forget about Stegron and use his costume to camouflage himself from him, as there is something more important to be done than fighting him. Spidey acquiesces and activates something in his costume that renders him transparent and undetectable by Stegron, who simply walks right past him. With Stegron out looking for him, Spidey follows Reed’s instructions and makes his way three floors down to the source of the radiation that is affecting everyone. There, Spidey finds the rock of life. Using the malleable quality of his costume's "smart" metal, Spidey wraps part of his suit around the asteroid, which will hopefully insulate its radioactivity. Within seconds, Stegron comes crashing through a wall, screaming at him about what he just did to the rock of life. Stegron grabs hold of the rock, which is still wrapped up in part of Spidey's costume, and hugs it to his chest, calling it his "gift to the world". As Stegron sobs about his failed dreams, Spidey realizes that it was him that brought the rock to New York City in the first place. Furious, Spidey gives him a hard time about it, because of all the lives that were lost because of the asteroid, and then proceeds to punch him with all his might with an uppercut to the jaw. Stegron is sent flying to the floor, where he continues to weep. Spidey tells him that he could cripple him, or even kill him right there and then, but he won't, because he is not an animal. As Spidey concludes his little speech, Puma and the Black Cat arrive on the scene to check up on him.

ACT 5: A short time later, Mister Fantastic arrives on the scene and takes the rock of life back to his headquarters where he puts it inside a containment unit. Meanwhile, John Jameson is released, Puma and the Black Cat "get it on", Vermin is somewhere inside a cage, and Dr. Curt Connors (the Lizard) is reunited with his son Billy, while Peter Parker and his wife Mary Jane watch on.

ACT 6: A little while later, Peter and Mary Jane are walking along a street. MJ tells Peter he did good but Peter can't shake the feeling that something is very very wrong in the world. Inside her apartment, Madame Web couldn't agree more and adds that Peter's life is about to get much more complicated.

To be continued.