William and Libby experience personal tragedy. Masters decides to pair Austin with a stranger. Virginia struggles with her parenting due to her long hours. Ethan's relationship with Vivian takes the next step, whether he likes it or not.

Virginia and William ramp up their participation in the study. Libby bypasses William and pressures Ethan to resume the treatments. Austin and Margaret ramp up their tryst leading to differing expectations. Ethan decides to commit to Vivian.