A young woman named Frances McCullen, grieving the loss of her mother and wrestling with the loneliness of living in New York City, discovers an abandoned handbag on the subway. Driven by her benevolent instincts and against the advice of her friend Erica, Frances takes it upon herself to return the bag to its owner rather than leave it with the lost and found. Her search leads her to the doorstep of Greta Hideg, an eccentric and seemingly lonely widow with a penchant for classical music and an endearing French accent.

Pleased to have her bag returned, Greta invites Frances in for coffee, sparking a friendship rooted in mutual loneliness. The relationship begins innocently, with Frances being drawn to Greta's maternal charm, filling the void left by her own mother's death. Greta, on the other hand, finds company and delight in Frances's youthful energy. As they spend more time together, their bond grows, with Greta offering a comforting presence and Frances providing companionship. However, the nature of their budding friendship takes a disturbing turn when Frances discovers that Greta may not be the benign figure she presents. This revelation triggers a series of events that unveils Greta's true nature and the dark intentions behind her gesture of lost and found.