Mara (Rosamund Pike) runs a guardianship company. She specializes in finding elderly people who are in poor health and helpless. She becomes their legal guardian through not-so-legal means, sends them to nursing homes, and then takes over and sells their property and real estate, and then takes the proceeds for herself. One day, Mara puts her next "devouring" target on an old lady named Jennifer (Dianne Wiest). After investigation, Jennifer has no relatives and has a valuable inheritance. She is simply their best "fat sheep". After some operations, Jennifer's mobile phone was confiscated and she was locked up in a nursing home, but what Mara and her lover and partner Fran (Eiza González) don't know at this time is that they have provoked someone who should not and should not be provoked.