As Noah’s life hangs in the balance, Samuel prepares to kill thousands and Peter and the others must band together to stop him and save Emma.

Fueled by his vision of Emma in grave danger, Peter attempts to rescue Sylar from his worst nightmare. At the carnival, Samuel reveals H.R.G.s secret past in order to bring Claire to his side. Meanwhile, Lauren makes a bold move to put a stop to Samuel.

H.R.G. enacts his plan to take down the Carnival with the help of Lauren and Suresh. Sylar visits Matt looking to understand his desire to make a human connection, but Matt has a plan of his own. Meanwhile, Peter warns Emma of Samuel’s intentions after his grim vision of the future.

Sylar visits Claire, while Hiro’s past decisions manifest subconsciously due to his brain tumor. Meanwhile, Samuel tries to impress Vanessa, his long-lost love, but things don’t go as planned.

While Hiro and Ando attempt to save Suresh, Bennet tries to expose Samuel’s weakness in his attempt to defeat the carnival leader.

Claire joins the carnival but begins to suspect Samuel has a secret agenda. Bennet recruits Matt in his battle against Samuel, while Hiro goes to help a friend.

As Claire becomes immersed into the world of the Carnival, she becomes increasingly suspicious of Samuel’s motives. Hiro is on a mission to rescue one of his own, but has difficulty communicating his intentions to Ando. Samuel has his sight set on Emma and her ability to complete his master plan. Meanwhile, Sylar returns to the Carnival in search of answers and Peter continues to struggle with the loss of his brother.

Noah has a surprise run-in with visitors; Samuel makes progress on his plan; Peter goes to extremes to obtain what he wants; and Claire comes to an unexpected destination

H.R.G. hosts an untraditional Thanksgiving dinner. Elsewhere, the Petrelli family gets a surprise guest at their table. Meanwhile, Samuel continues to hold Hiro hostage, as Lydia goes in search for the truth.

Samuel learns just how powerful he can become and takes dangerous measures to reach his full potential. Meanwhile, as Tracy begins to lose control of her ability, one of her own comes in harms way. Elsewhere, Sylar continues his battle with Matt.

Claire is determined to get to the bottom of the Sorority Rush attacks on her own, until H.R.G. intervenes only to realize he may be the source of her troubles. Meanwhile, Peter’s new ability is a perfect fit for his job and gives him the opportunity to help Emma accept her new life. Elsewhere, Sylar’s battle at gaining full control over Matt’s body escalates –with potentially dangerous implications at stake

When Hiro travels three years into the past, he has a second chance to save Charlie from the hands of Sylar. However, Samuel’s presence serves to complicate Hiro’s mission even further. Elsewhere, H.R.G.’s past with his Primatech partner is revealed.

When Hiro (Masi Oka) travels three years into the past, he has a second chance to save Charlie (guest star Jayma Mays) from the hands of Sylar (Zachary Quinto). However, Samuel’s (Robert Knepper) presence serves to complicate Hiro’s mission even further. Elsewhere, H.R.G.’s (Jack Coleman) past with his Primatech partner (guest star Elizabeth Rohm) is revealed.

Under Samuel’s guidance, Sylar starts on a path to rediscover his true identity. Hiro helps Emma accept and understand the great possibilities that go along with having an ability. Meanwhile, Peter enlists HRG to help him find a healer who can save Hiro’s life.

Samuel prepares for new additions to his family, while Lydia warns him of the consequences. Claire discovers that her roommate Gretchen may have a hidden agenda. Meanwhile, Peter finds an unexpected way to connect with Emma, who would prefer to stay distant. Elsewhere, a different side of Sylar emerges as he desperately tries to remember the person he used to be.

As Hiro’s life continues to hang in the balance, he distracts himself with saving the lives of others. Meanwhile, Angela tries to help the new “Nathan” remember his past, at the risk of his remembering too much. Elsewhere, Tracy is determined to get her old job back, but soon realizes that she needs to make more of an impact.

Peter deals with repercussions from his heroic acts and meets a new woman with abilities (Deanne Bray); Claire deals with the unveiling of her secret; Samuel goes to great lengths to retrieve memories of his brother; and Matt battles inner demons as Sylar reappears.

Claire garners attention at college following an odd death in the fourth-season premiere.