With missing friends and mysteries abound, Liz returns to fringe science, but in working alongside her new mentor, she's confronted with an unsettling revelation and a difficult choice, meanwhile, Maria uncovers the truth behind the "messages" she's been receiving. Elsewhere, the bond between brothers is tested when Max keeps an explosive secret from Michael, putting them at odds during a critical moment. Lastly, Isobel tries to pull answers out of Tezca, only to discover that the villain in her story is not as clear-cut as she may seem.