Sherlock and Joan investigate the disappearance of Abby Campbell, a lab technician at Joan's old hospital. Sherlock quickly figures out that she is, in fact, dead, and her skeletal remains were set up like a laboratory specimen.
Abby's husband Nate, an oncologist at the hospital, denies killing her and says that she was dying anyway of pancreatic cancer. A theory that Abby was having an affair with another Doctor, Branford Fisher, is shot down when they realize that Branford is actually part of a group marriage with Nate and Abby.
An interview with members of Abby's previous group marriage leads them to a researcher who said that she wanted to do an off-the-books blood test. They realize that she was testing blood from members of her cancer support group.
After meeting with one of these individuals, Joan discovers that she and many others were purposefully misdiagnosed with cancer by Nate Campbell, who murdered Abby when she started to grow suspicious and confronted him.
Meanwhile, Joan learns that a detective from the Coney Island Burglary division is investigating her, questioning all her friends and generally stalking her. Joan does a little investigation of her own and discovers that Detective Cortes has a personal grudge against her.
They work out their differences in a boxing match, which Joan ultimately wins.