Antonio and Laura are called to the scene of a murder. A woman's body has been found with maggots crawling on it. There is a bloody baseball bat nearby. The cops quickly learn that the lady was pregnant but see no sign of the baby.
The pregnant woman's name was Julia Keyes and she attended a yoga group for pregnant women. One of the women remembers that Julia's ex-husband was named Ryan Mattis. Ryan is a wheelchair user living with his girlfriend, Amber. Amber doesn't want to hear about Julia, who she thinks was obsessed with Ryan.
The investigation continues and Stone is shocked to find out that DNA evidence at the scene points to David Zachariah, a serial killer he put away for murder at the beginning of his career. Stone goes to see Zachariah, who is creepy and threatening but gives him nothing useful.
Antonio and Laura confront Ryan, having found out he talked to Julia shortly before her death. Amber confesses to having taken the call and erased it from Ryan's call log while he was asleep. Julia said she was pregnant and Amber arranged to meet her, then told her to stay away from Ryan. Amber saw Julia with another pregnant woman.
The detectives realize the other woman was Dawn, one of the women at the group. When they go to her home they find her holding a dead baby and comforting it as if it were alive.
Dawn is arrested for the murder of Julia and her baby but her lawyer claims insanity. Dr. Charles interviews Dawn ,who talks about how she was brutally raped at 11 and her Fallopian tubes had to be removed. She found out when she was 13. Her father let her go on a date with a boy and when she came home she heard him yelling at her mother that it wasn't like she could get pregnant. She was devastated. She believed her role as a woman was to have children.
DNA evidence reveals that Dawn is Zachariah's daughter, which shocks Stone because Zachariah killed all his victims. However, before trial Dawn's mother talks to Stone. She tells him she was raped by Zachariah and when she became pregnant she let her husband think the baby was his.
At trial, the defense attorney claims Dawn's behavior was involuntary and dictated by having DNA of a serial killer. Stone thinks this is ridiculous but the judge agrees to hear the argument. At trial, Zachariah says he killed all the women he was accused of killing except for the one he is locked up for, Alice White, and that he has irresistible urges to kill women. Dawn testifies to having similar experiences and claims that she is the one who killed Alice White and her father lied to protect her.
Stone and Valdez think this is BS but Jeffries says they have to prove it because the existence of genes is a scientific fact. Stone cross examines Dawn and proves she was trying to save the baby's life, not kill it, and that she killed Julia because she wanted her baby.
Zachariah attempts to get his conviction vacated on the basis of Dawn's testimony after she is found guilty of murdering Julia, but Stone successfully argues that his plea bargain should be vacated as well and gets him extradited to Indiana to stand trial for the nine murders he confessed to on the stand.
Meanwhile, Laura attempts to get custody of her child back but the judge refuses to grant it because she thinks she is not stable enough due to her work schedule and her ex's false claim that she's a drug addict.