Emil Danko comes to Noah for help when Tracy Strauss returns and starts killing his men. Claire starts college in earnest, while "Nathan" begins to discover he isn't quite the man he thought. Hiro and Ando open a heroes-for-fire business, with unexpected consequences.

Hiro meets a mysterious carnival man 14 years in the past, and is prompted to change history. Noah calls on Peter to help pursue a lead from Danko, and runs afoul of a knife-wielding speedster from the carnival. Matt Parkman is confronted by a piece of Sylar in his mind, and Claire is stunned when someone close to her appears to have been murdered.

Samuel, the carnival leader, goes under cover to manipulate Peter, threatening him with a lawsuit. Matt continues to fight the piece of Sylar in his mind while he and his partner search a suspected drug house. Claire deals with her new friend's discovery, and a deaf woman discovers she has a new ability.

Haunted by newly unearthed memories of his youth, Nathan Petrelli seeks closure about the mysterious disappearance of an old girlfriend. Tracy returns to her old boss in the hopes of getting her life back, while Hiro makes the most of his last days by trying to stop a coworker from jumping off the roof.

Samuel seeks to bring another person into the carnival's family, while Peter has another encounter with Emma. Claire grows suspicious of her new roommate, and Sylar shows up on a road side with severe amnesia.

When Hiro turns up on Peter's doorstep, Peter takes it upon himself to find a way to save his life, turning to Noah to locate a healer. Samuel helps Sylar recover his identity, and Hiro tries to help Emma realize the benefit of her ability.

Bennet calls in Tracy to help young Jeremy Greer, who is suspected of killing his parents. Claire and Gretchen and subjected to sorority hazing inside a slaughterhouse, and Matt faces new threats from the Sylar in his head.

Hiro returns to a Texas diner three years ago to try and save the love of his life from Sylar, and finds that Samuel is there with his own agenda. Noah considers crossing a line with his partner.

While Claire and her father decide how to protect her roommate from Becky, Samuel goes to speak to Claire. Now in control of Parkman's body, Sylar heads for New York. Peter uses his new ability to heal accident victims, but it takes its toll.

Nathan and Peter seek to unlock the secret of Nathan's identity crisis, while Tracy loses control over her power. Nine weeks in the past, Suresh makes a discovery about a man who can amplify his powers, leading to a fateful meeting.

Peter and Nathan confront their mother about their discovery, while Noah brings an old friend to the family Thanksgiving. Lydia, one of Samuel's followers, asks for Hiro's help to learn the truth about Joseph's death.

Noah and Lauren try to locate Claire, who has gone to Samuel's carnival. Peter takes on Sylar, using the Haitian's power to gain the upper hand and try and save Nathan.

Claire grows increasingly suspicious of Samuel when she learns that he is using Primatech files to locate people with abilities. Ando tries to make sense of Hiro's newfound mission, and Samuel enlists Emma's help to locate someone.

Peter and Claire struggle with the death of a loved one, while Noah interrogates Edgar the speedster for information. Sylar returns to the carnival with a vengeance, but finds Samuel more than a match for him.

Hiro and Ando enter a mental asylum to rescue Mohinder, while Noah targets a woman from Samuel's past to try and capture him. Emma explores a new discovery about her power.

Pushed to the brink of death, Hiro finds himself on trial and accused of using his abilities for personal gain. Sylar seeks out Claire for answers about who he ought to be, and Samuel tries to win over the love of his life.

With Noah and Lauren closing in on Samuel's carnival, Claire acts to try and protect innocent lives by convincing Samuel to surrender. Convinced he must give up his powers, Sylar turns to Matt Parkman for help.

Trapped in a vacant city inside Sylar's mind, Peter and Sylar must work together to escape. Meanwhile, one of Samuel's people uses his ability to reveal Noah's secret past to Claire. Lauren faces Samuel directly.

With Noah and Claire buried alive, Samuel moves the carnival to Central Park with a plan to kill thousands. Matt tries to stop Peter from taking Sylar, and Hiro finds Charlie in an unexpected place.