After a violent tremor shakes a Manhattan office building to its core, leaving only one survivor who leads the Fringe Team to believe he is not from this reality. Walter surmises that what shook the building was not geologic, but rather something discovered by him and William Bell many years ago. With another catastrophe imminent, the team races to Jacksonville, the site of Walter and William’s experiments, forcing Olivia to face her mysterious past in an effort to save hundreds of people from certain death.