In the stunning first season finale, Olivia traveled to an intriguing parallel universe where she met Massive Dynamic founder William Bell. Season Two opens with Olivia's shocking return to this reality, and Peter, unknowingly in a race against time with an ominous mobile force, pursues information about Olivia's perplexing visit to the alternate reality. Meanwhile, Walter reenters the lab to cook up a bit of fringe science, and of course, some custard for someone's birthday.