Nathan finds Peter standing over Arthur's corpse. Peter admits that Sylar did it; there was no other way to end it. Now the formula has to be destroyed. Nathan explains that it's too late; he's going to finish what Arthur started. Twenty marines have already been injected with the formula. Peter tries to shoot Nathan, but he can't, so he knocks him unconscious instead.
Back at Primatech, H.R.G. summons Meredith. Now that Arthur's dead, Peter will need their help. They're joined by Angela and Claire, just as the lights flicker off, and bars slam down over the windows. Sylar is back and he's put Primatech on lockdown. Holed up in the security office, Sylar broadcasts over the PA: tonight, he's going to prove to them all that they're monsters, just like him.
H.R.G. hands Claire a shotgun, telling her to protect Angela at all costs. He and Meredith are going after Sylar, who gets to work on Claire, reminding her that the others betrayed her. Angela doubts they can stop Sylar, but Claire is confident she can. There's a vulnerable spot on the back of her head; if something was jammed in there, her brain would shut down. Sylar must have the same vulnerability.
Matt thinks that Hiro can't cause any trouble, since he's still stuck in time on the flag pole. Daphne's not so sure -- if Hiro dies, the past could change the present. Ando, Matt and Daphne proceed to Mohinder's empty lab, hoping to find him, but no dice. Daphne figures that Mohinder is at Pinehearst and rushes off to get him.
Another entry in Mohinder's log: time is running out. The infection in his lungs is fatal. Injecting himself with the formula is his only hope. Peter appears to hold Mohinder at gunpoint and announce his intention to destroy the formula. In a sudden whoosh, the EpiPen of formula vanishes out of Mohinder's hand. Furious, Mohinder attacks Peter, only to be stopped by Flint, who threatens to burn his face off.
Knox offers to help destroy the lab, confusing Peter. Flint explains: if the formula works, then those who already have abilities will no longer be special. Mohinder protests -- not only is the formula highly combustible, but Peter is siding with these villains over Nathan, who only wants to do good? Peter begins to destroy the lab, explaining that Nathan isn't in charge anymore.
Soldier Scott enters Arthur's office just as Nathan revives. He reports that Tracy stopped the injections, so Scott is the only one who's received the formula. Scott promises to stop Peter, but Knox snaps his neck in a flash. Smiling, Knox admits that he's working for Peter, who's one of the good guys now.
Daphne returns to Mohinder's lab with the EpiPen of formula. Matt tries to stop Ando from injecting himself -- what if he gets some freak ability? Daphne reasons that she wanted to run, and Matt wanted to know what everyone was thinking -- look how their abilities turned out. Asking Matt if he's ever had faith in something despite all odds, Ando slams the EpiPen into his arm and passes out.
Hiro manages to haul himself off the flag pole and back into his father's apartment. There he spies a depressed little Hiro, and asks for his help in retrieving the paper containing the formula. Meanwhile, Claire holes up with Angela. Sylar calls to offer a choice: if Claire kills Angela, he'll allow her to walk away with H.R.G. and Meredith. Sick of Sylar's crap, Claire shoots the phone.
Meredith can't believe that H.R.G.'s plan to unlock the Level 5 captives (Doyle, Echo and Pine) is a good one; the inmates want to kill them as much as Sylar does. H.R.G. offers to free the man who brings him Sylar's head. When Doyle asks what's to keep them from escaping, H.R.G. explains that Sylar will -- they're all locked in together. Meredith realizes that H.R.G. is using the inmates as bait to flush out Sylar.
When Ando finally comes to, he sets to the business of trying to time travel, but even squinting his eyes like Hiro doesn't work. Unaware that electricity is simmering from his hands, Ando pounds a table, resulting in a shower of red sparks. Back at Primatech, Sylar makes quick work of Pine and Doyle, then surprises Meredith, jamming a hypodermic of adrenaline into her chest.
H.R.G. nearly trips over Echo's corpse, on his way to find Meredith hiding in Flint's Level 5 cell. Breathing heavily, Meredith warns H.R.G. that she can't control her ability, just as Sylar locks them both into the cell. Sylar has left one bullet in H.R.G.'s gun, which he can use on Meredith before she burns him to death. What lie will H.R.G. tell Claire about all this?
Nathan tells Knox that he's backed the wrong horse. Peter always winds up losing in the end. Knox is surprised that Nathan hates his brother so much. Is he afraid that Peter will top him? Claiming he's not afraid of anything, Nathan attacks Knox, but it's not long before Knox has the upper hand. Just as he's about to deliver the death blow, Knox freezes and shatters into a million pieces, courtesy of Tracy.
Matt puts his hands on Ando and doubles over, his mind overwhelmed with voices. When he comes around, he explains that it was like he could hear every thought in the city. When Daphne touches Ando, she goes back a few minutes in time. Meanwhile, Claire drags Angela down the hall towards Level 5. When she lets go of Angela for an instant, Sylar steps in to taunt Claire about her allegiance to H.R.G.
Claire runs for Level 5, but is unable to open the cell, since Sylar ripped the keypad out of the wall. H.R.G. instructs Meredith to heat up the glass wall, then tries to shoot it out, but no go. Claire takes a dive through the window, shattering it. She pulls a large shard out of her neck as H.R.G. exhorts her to run. When Meredith tells them to go ahead, Claire promises to come back for her.
Tracy wants to get Nathan out of Pinehearst before the situation becomes something she can't spin. Despite her plan to take the formula and start over, Nathan refuses to run away. When Tracy reminds him that he hired her because she's a realist, Nathan fires her. Meanwhile, Matt deduces that Ando's new ability is to act like a supercharger. Realizing she can time travel with Ando's help, Daphne takes his hand and takes off.
Little Hiro has just helped Hiro open the safe to reveal the formula, complete on one piece of paper. Sending little Hiro to bed, Kaito confronts Hiro, then attacks him with a sword. Claiming the formula must be destroyed, Hiro rips the paper in half. Just as Kaito is about to administer a death blow, Hiro disappears in a whoosh! Back at the lab, Hiro isn't grateful that Daphne and Ando saved his life. He has to get back to destroy the formula!
Tracy cracks the safe in Arthur's office, and is just pulling out the two halves of the formula when Hiro and Daphne show up. When Tracy calls Hiro "Pikachu," he punches her and grabs the formula, impressing Daphne. Meanwhile, Peter and Flint overturn a vat of formula which washes over Mohinder, healing him. Flint flames up, determined to blow the place up, panicking Peter, who's worried about Nathan.
Nathan takes Flint out with a pipe, then starts in on Peter, who has broken his heart. As the fire rages, Peter finds one last EpiPen of formula and stabs himself in the leg, then flies Nathan out the window as the lab explodes. Meanwhile, Sylar has questions for Angela, explaining he'll know if she's lying. Angela admits that she's not his mother, and she manipulated him because she needed a killer. If Sylar kills her, he'll never find out who his real parents are.
Sylar screams for the truth, allowing Claire to sneak up on him and plunge the glass shard into the base of his brain. As Sylar goes down, the lights come on and lockdown is over. H.R.G. rushes in -- they need to leave. Claire insists on going back for Meredith, who explains that it's too late. She urges Claire to run as she's engulfed in flames.
Peter lands in the woods. Nathan can't believe that Peter took the formula, but Peter explains he had no choice; he had to save Nathan. That's not what Nathan would have done. Nathan flies off, as a healed Suresh lopes down the freeway. Tracy pulls up and motions him into her car. Victorious, Hiro rips up the formula, while Claire, H.R.G. and Angela watch Primatech burn.