Samples of a lethal viral disease vanish, a dire development that pushes Allison to tap into her extrasensory ability to foil a possible large-scale bioterrorism attack. Meanwhile, Scanlon prepares to pop the big question to Lynn (Tina DiJoseph), but Bridgette's visions indicate that their relationship could meet an ill-destined end
Odd things occur for Allison, starting with her new sensitivity to light and the fact that the sunglasses she wears shows mysterious numbers that can tie into people's life expectancies. Like that wasn't enough, Allison has a dream about Joe's dad, causing Joe to begin taking better care of his health.
On the 100th episode of Medium, an infant is kidnapped and Allison investigates the disappearance. But when she becomes too obsessed with the infant, Joe starts to get worried about her. Meanwhile, Bridgette and Joe are surprised after Marie manages to play the clarinet without any issues even though she hasn't attended any classes, while Bridgette is struggling to play.