After an unexpected, whirlwind romance, quiet librarian Martha married Alan. But when she thinks she sees his mask slip, she starts to fear that the conferences he travels the country to attend might be a cover for something far more sinister. As she secretly starts to map his movements she unearths a string of dead women, but could these two things really be linked? Unsure of her own instincts, Martha turns to an old friend, Lily Kintner, who once helped her escape a toxic relationship in grad school. But what Martha doesn't know is that Lily has a dark side of her own.