Detectives Robert Goren and Alexandra Eames investigate a diamond heist in a house that left its two occupants and one of the robbers dead. Karl Atwood, the criminal who planned the heist, attempts to trick the police into thinking that the robbery was mob-related, but the detectives uncover the deception when they track down a lead that shows that he served time in a Canadian prison, and has skipped parole and crossed the border. Goren and Eames interview Atwood's girlfriend, Gia, and tell her that he was infected with AIDS in prison, and that he has passed it on to her. They promise to be lenient on her and get her treatment if she will help them to apprehend Atwood. She arranges to meet with Atwood, and when the buyers for the diamonds arrive at a hotel, Goren and Eames arrest everybody. They inform Gia that she has not contracted AIDS.

The Major Case Squad team investigate the murder of Lois Romney, a pregnant woman who has given up her drug addiction and is struggling to stay clean. It initially appears that the murderer is the victim's unstable junkie boyfriend, Dale van Acker, and Captain Deakins tells Goren and Eames to close the case. Deciding that the death of a pregnant woman deserves more attention, their investigation leads them to the boyfriend's wealthy and domineering socialite mother, Priscilla van Acker, and his stepfather. Goren suspects that Priscilla is a sociopath, who disapproved of her son's girlfriend, plotted to kill her and framed her son.