After discovering a handbag on a New York subway train, Frances McCullen (Chloë Grace Moretz), a young woman bereaved by her mother's death, sets about returning it to its rightful owner. Frances subsequently strikes up an unusual friendship with enigmatic widow Greta Hideg (Isabelle Huppert), much to the dismay of her best friend Erica Penn (Maika Monroe) who is helping Frances acclimate to the city. Frances ignores her friend's concerns, but Greta's motives may be more sinister than they initially seem.