Denial

S3, E21: The sexual assault of a heroin addict (guest star Martha Plimpton) leads Detectives Benson (Mariska Hargitay) and Stabler (Christopher Meloni) to the gruesome discovery of a decomposing baby's finger in the victim's purse. As they search for both the rapist and the identity of the baby, the detectives find that their assault victim might be withholding information to protect her icy mother (Oscar-winning guest star Mary Steenburgen) or her protective grandmother (Oscar-winning guest star Estelle Parsons).