Claire struggles with adjusting to her new life in college when a mysterious death thrusts her into the spotlight once again.
While the heroes adjust to new surroundings, a mysterious carnival clan, led by ringleader Samuel, sets their sights on familiar faces; meanwhile, Peter is called upon to aid an old friend.
Peter meets a reluctant new hero; Matt struggles with his internal demons as Sylar resurfaces; and Samuel attempts to recapture his late brother's memories. Louise Fletcher guest stars.
As Hiro’s life continues to hang in the balance, he distracts himself with saving the lives of others, and Angela tries to help the new "Nathan" remember his past.
Samuel prepares for new additions to his family; Claire discovers her roommate has a hidden agenda; and Sylar desperately tries to remember who he used to be. Tessa Thompson guest stars.
Sylar begins his journey to find his identity, and Peter enlists H.R.G. to help find a healer who can save Hiro’s life. Ray Park guest stars.
Matt goes to extreme measures to extinguish Sylar, who continues to torment him, and H.R.G. calls in a favor from Tracy. Tessa Thomson and Madeline Zima guest star.
Hiro gets a second chance to save the love of his life from Sylar, but Samuel's presence complicates the mission. Jayma Mays and Elisabeth Rohm guest star.
Claire learns the truth behind the sorority attacks, and Sylar's battle to gain control over Matt's body escalates. Jimmy Jean-Louis and Tessa Thompson guest star.
Samuel learns just how powerful he can become and takes dangerous measures to reach his full potential; Tracy begins to lose control of her ability; and Sylar continues his battle with Matt.
H.R.G. hosts a nontraditional Thanksgiving dinner; the Petrelli family gets a surprise guest at their table; and Samuel continues to hold Hiro hostage as Lydia goes in search of the truth.
Samuel's grand plan begins to come to fruition; Peter struggles to accept the truth and takes extreme measures to get what he wants; and Claire's journey leads her to an unexpected destination.
The search for answers intensifies as final respects are paid to a fallen hero. Dawn Olivieri guest stars.
Sylar returns to the carnival in search of answers, and H.R.G. sets his plan in motion to take down the carnival. Ray Park and Dawn Olivieri guest star.
H.R.G. exposes Samuel's greatest weakness in an effort to stop him, and Hiro and Ando go to extremes to save Suresh.
The verdict of an unexpected trial could mean the end of Hiro, and Sylar pays Claire an unexpected visit. George Takei and David Anders guest star.
The tables are turned as H.R.G. attempts to gain the upper hand, and Peter warns Emma of Samuel’s intentions. Ray Park and Dawn Olivieri guest star.
Sylar's worst fears come to life as H.R.G faces his past. Eric Roberts, Madeline Zima and Elisabeth Rohm guest star.
In the climactic season finale, everyone bands together to stop Samuel from taking the lives of thousands. Ray Park guest stars.