Four months after the confrontation with Sylar, the Bennet family tries to start anew in a new city, while the Petrellis recover from a devastating loss. Hiro meets his boyhood hero in feudal Japan, and a brother and sister try to make it north to America.
Hiro dons his hero's armor to try and set history on the right path. An amnesiac Peter finds himself a prisoner of a family of Irish mobsters. Maya's abilities continue to prove dangerous, and Claire becomes increasingly frustrated with her secrets.
Sylar awakens to find that an unfamiliar face is helping him recover. Hiro helps Kensei live up to his legend, even though it means losing the woman he loves. As Niki and Micah leave Las Vegas to start a new life, Mohinder returns to New York. Maya tries to spring her brother from a Mexican jail, and Claire's secret is discovered.
After Angela Petrelli confesses to a murder she didn't commit, Parkman pushes to continue his investigation -- and makes a startling discovery about his own father. Micah's cousin Monica struggles to support her family in New Orleans, and Maya and Alejandro pick up a dangerous passenger.
Nathan and Matt go in search of Matt's dangerous father, only to be trapped inside their own nightmares. In New Orleans Monica struggles over her newfound ability, and a young woman arrives in Ireland looking for Peter.
Bennet takes the Haitian to find his former mentor, while Claire and West decide to teach the school's head cheerleader a lesson. In feudal Japan, Hiro and Kensei attempt to rescue the Swordsmith. Suresh faces a moral dilemma after introducing Monica to the Company, and Sylar and the twins attempt a border crossing.
With the "Nightmare Man" coming for him, Bob tells Parkman that he is the only one who can stop the enemy. In the near future, Peter and Caitlin discover that a virus has wiped out most of the world's population. West discovers that Claire's father is the one who abducted him, and Hiro has one final chance to set history right after his own hero betrays him.
Following the explosion over New York City, Peter and Niki are both brought into the care of the Company. Peter meets a man named Adam, who convinces him that he has become the Company's prisoner. Disaster strikes when Maya's ability manifests during her brother's wedding celebration.
Bob sends Mohinder and Elle on a mission to capture Claire and take out her father -- but Mr. Bennet isn't going down without a fight. Matt begins to explore the true extent of his ability, and Hiro goes back in time to try and save his father.
Peter and Adam track down a former Company scientist in order to find the Shanti Virus, though Peter does not know his new friend's true colors. Sylar tries to get rid of Maya's brother, and Micah is reunited with his mother. Monica uses her power to try and help her cousin.
Peter and Adam infiltrate Primatech to find the virus that will wipe out most of the world's population, but Nathan and Matt try to stop them. Hiro goes after Adam for personal revenge, while Claire plans to expose the Company. Micah asks his mother for help after his cousin is kidnapped while trying to be a hero.
