Peter: Not much work for him this week. We pick up where we left off last week, as Peter is holding Sylar against the wall in Level 5. When Angela walks in, she diverts Peter's attention in time for Sylar to knock him out cold. Angela then puts him into a medicated coma and he remains in Level 5.
Mohinder: The bad doctor does his best impressions of Dexter: can't fight his urge to kill. He slays a random drug dealer and then drags him back to a room in his lab, where Mohinder somehow sticks the murdered dude into a gross web-type thing on the wall. Later on, Maya sneaks in and finds Mohinder's kills. When Mohinder finds Maya in his special, evil room, he kills her. To repeat: MOHINDER KILLS MAYA! Thank you.
Hiro/Ando: These two immediately lose Adam Monroe. He takes them to a bar in order to find out who Daphne is working for and to recover the formula (why did Angelia think Adam could help them? That will likely remain forever unclear). But he basically outsmarts the duo and escapes... only to be captured by Knox.
We later learn than Knox is working with Daphne, who returns to the bar with her new pal and asks if Hiro and Ando wish to join their (villainous) cause. They say yes, which was confusing and unexpected. In order to prove how "bad ass" he is, Hiro sticks a sword through Ando, per the orders of Knox. For the time being, it appears as though Hiro killed his friend out of necessity to save the world (this reasoning, and entire story line, made little sense to us, too; but we're certainly guessing Ando won't remain dead for long).
HRG/Sylar/Claire: This was great stuff. Claire is on a mission to take down villains. She follows the file on a man named Stephen and at first tries to take him to Level 5. But Stephen quickly takes Claire's gun from her via his power: the creation of a vortex that sucks up everything in its path... forever. This was how Knox accidentally killed a man years ago. He tells Claire his story and makes her realize that now all villains are actually evil; some are actually confused, like her.
Claire helps Stephen locate his family... when HRG and Sylar (working as a team again) enter the picture. Stephen uses a vortex to escape, but Claire trusts that her father will merely talk and reason with the suppose baddie, so she reveals his destination: when HRG eventually finds Stephen again, he holds a gun to his head, but is willing to make a deal: use the vortex to make Sylar (who is standing yards away, keeping watch) disappear and HRG will let Stephen go free.
Claire tries to plead with her dad, but to no avail. Stephen, not wishing to become a monster, creates a vortex and kills himself with it. Pretty well done. On the drive home, Sylar is trying to convince Claire that her father cannot relate to those with abilities. He sees them all as monsters. While Claire doesn't trust Sylar, she definitely has questions about her dad now.
Nathan/Tracy: When Nathan mentions that they owe their powers to God, Tracy tells him about the doctor that admitted to altering her and her sisters' DNA so many years ago. Nathan confronts his mother about this and Angela eventually admits that The Company did experiment on babies - and Nathan was one of them. This shatters his belief that God was responsible for everyone's powers, as he and Tracy leave Angela's office discouraged. They decide to visit Suresh and to see if he can help, not knowing that he's become (we don't learn about this visit this episode).
Mr. Petrelli/Mr. Parkman: Yes, you read those characters' names correctly. Near the end of the episode, Daphne speeds over to a facility named Pinehurst. She speaks with Linderman, who says she's done a solid job organizing a team of herself, Hiro, Monroe, Knox; your basic villains. He says she has one more person to recruit: Matt Parkman.
After Daphne departs, Maury Parkman enters the picture. He walks into a hospital room and is seen talking to someone seemingly being kept alive by machines. He says that he successfully made Nathan and Daphne see visions of Linderman (remember Maury's power to mess with one's mind?) and that an army was being built, as requested. And just who made that request? Who is lying in the hospital bed, communicating with Maury via his thoughts?
Source: TV Fanatic