In Ireland, Peter attempts to move beyond the past, but discovers that a mysterious woman -- Elle -- is willing to kill to find him. Matt and an unexpected ally fly to Philadelphia to hunt down the nightmare man, following his terrible attack on Molly, but the pair finds themselves outmatched. Monica tries to come to terms with her new abilities and her role as a local hero. Suresh meets his new partner and gets a disturbing assignment. H.R.G. takes a step to further protect his family. Meanwhile, as Hiro continues to fix the past in feudal Japan, Ando attempts to piece together historically what's happened to his best friend.

When one of his forgotten abilities suddenly manifests, Peter and Caitlin get thrown into a crisis situation, and learn first-hand just how deadly the mysterious virus striking people with abilities can be. Suresh, Matt, Nathan, Niki and Bob band together to fend off the "nightmare man's" attack. When West drops by the house, Claire attempts to hide family photos that reveal the man who kidnapped him as a child is her father. Meanwhile, in feudal Japan, Hiro and Kensei's legendary journey takes a dramatic, final turn.