Kelsey pays tribute to her late mother by preparing for a marathon and documenting her progress online. Her updates catch the attention of Billy (Keenan Tracey), a grocery store employee who cares for his disabled mother, Debbie. Driven by obsession, Billy abducts Kelsey and confines her in their attic, keeping her captive for several years. When Debbie uncovers the horrifying secret, she and Kelsey join forces to struggle for their freedom and survival.