Trapped in a violent, controlling relationship with a wealthy and brilliant scientist, Cecilia Kass (Elizabeth Moss) escapes in the dead of night and disappears into hiding, aided by her sister, their childhood friend and his teenage daughter. But when Cecilia’s abusive ex (Oliver Jackson-Cohen) commits suicide and leaves her a generous portion of his vast fortune, Cecilia suspects his death was a hoax. As a series of eerie coincidences turns lethal, threatening the lives of those she loves, Cecilia’s sanity begins to unravel as she desperately tries to prove that she is being hunted by someone nobody can see.