Ep 5. Conditions of Existence

Sarah is still struggling to make sense of the mysterious life of her doppelganger Beth. With the help of her foster brother Felix, Sarah poses as Beth to gain access to her apartment and learn more about her past. Inside, Sarah is confronted with tangible evidence of a seemingly perfect life; a loving boyfriend, a sparkling clean demeanor and bags of prescription medications. But Sarah's search for answers hits a snag when she realizes she's not the only one on the prowl. A mysterious blonde seems to be tracking her every move, and the encounter leads Sarah to a deadly game of cat and mouse. Meanwhile, Alison's paranoia is seeping into her everyday life, as she starts to question those closest to her. Her husband Donnie and best friend Aynsley both feel the pressure and are forced to come clean about their own secrets. And Cosima is forced to choose between science and morality when she finds herself ultimately responsible for a frightening new discovery.