A raid by public health officials uncovers Eric Greenwood's body. It's discovered that the victim was jealous of his boss Bob Munson's internet romance with a woman named Chrissy. Munson posed as a young Marine to attract her, and has been stealing so he can send money to her. Greenwood wanted Chrissy for himself, so he tried to tell her that Munson lied to her. The detectives go to "Chrissy's" address, which is actually the home of her mother Donna Cheponis (Melissa Leo). It turns out Chrissy has been a missing person for two years; but Cheponis inadvertently gives away that she knows about Munson. A search of her home reveals she bought a large amount of expensive goods with the money Munson sent.
Cheponis claims that Munson contacted her via Chrissy's social media. She found him so charming that she pretended to be Chrissy to keep talking to him. After speaking to Greenwood, she confronted Munson about his lies; she insists this must be why he killed Greenwood. However, phone records show Cheponis called Munson on the night of the murder and plotted to lure Greenwood. The prosecutors surmise she didn't want Greenwood scaring Munson away, or her scam would be over. Munson admits that "Chrissy" told him to kill Greenwood. He initially accepts a plea deal to testify against Cheponis but, in court, suddenly changes his story to deny she was ever involved.
The detectives learn that Cheponis instructed her boyfriend Carl Heckley to write to Munson and convince him he really was talking to Chrissy the whole time. Now Munson thinks he is protecting Chrissy by lying to keep her mother out of jail. Chrissy's remains are found in Heckley's basement; Cheponis killed her two years ago after finding out that Chrissy and Heckley were having an affair. Cutter shows Munson parts of Chrissy's skeleton and the medical records used to identify her. Forced to confront the truth of what's happened, Munson testifies against Cheponis and she is convicted of murder.
This episode contains examples of:
- Abhorrent Admirer: Munson sees Cheponis as this when he learns she was catfishing as her daughter "Chrissy" the whole time.
- Dating Service Disaster: The catalyst for the plot of the episode.
- Dead Person Impersonation: Donna admits to the police that she maintained her daughter's social media account, pretending to be her daughter. As it turns out, she had murdereg her daughter before doing this.
- I Never Told You My Name: Cheponis gives herself away by mentioning the name of Chrissy's online boyfriend, which Lupo and Bernard hadn't told her.
- It's All About Me: Cheponis' attitude.
- I Was Quite a Looker: Cheponis claims that she used to look exactly like her beautiful daughter; although given her excessive vanity, it's unknown if that's true.
- Murder the Hypotenuse: The real Chrissy was killed because she'd had an affair with Cheponis' boyfriend. It's also initially suspected that this was Munson's motive for killing Greenwood.
- Offing the Offspring: Cheponis turns out to have done this.
- Persona Non Grata: As per the episode's title.
