Logan and new partner Nola Falacci are called in to investigate the brutal murder of an Ob/Gyn. The victim, Zach Rush, ran a private fertility practice with his brother, also a doctor, Eli Rush. Eli, who found the body, admits to contaminating the crime scene with his own blood, while trying to resuscitate his brother. The graphic staging of the body, spread-eagle on an exam table, leads Logan and Falacci to suspect the killer may have been sending an anti-abortion message.
Logan and Falacci interview the office genetics counselor, Tom Pittino, who admits he had witnessed an angry outburst from a patient the day of the murder. The detectives find the angry patient, who claims he was upset about the doctor performing an abortion on his wife, who was carrying a baby with spina bifida. That suspect's alibi is confirmed by the wife, who reveals that Zach had admitted to having problems with his own son.
Logan and Falacci interview Zach's wife, Paula, and their son, Jason, who had fought bitterly with his father at a recent holiday dinner. Jason denies any wrongdoing, but when the detectives ask to see if he has cuts on his hands, he acts out, stripping off his shirt and throwing it at Falacci, inadvertently giving her a sample of his DNA. On the way out, Logan remarks to Falacci that the son's body language indicated he had a problem with his mother, Paula, who seemed like she had something to hide.
At the Squad Room, Logan and Falacci have uncovered suspicious behavior on Paula's part; an unexplained separate cell phone that calls an anonymous number. They bring Paula in, who tearfully admits she was having an affair with her brother-in-law, Eli.
Eli denies any involvement with his brother's death, and claims he had just broken up with his sister-in-law before the murder. In fact, Eli claims, he and Paula only got close when they bonded over the wayward behavior of Jason. Eli was acting like a father-figure to Jason, since he's incapable of having any children of his own, having been sterile all his life. Logan and Falacci check Eli's alibi with his date that evening, Kiki, but uncover a short, unaccounted-for window in his time line. Their suspicions of Eli take a new twist, when the DNA evidence from the murder comes in: blood at the crime scene is revealed to belong to Eli's biological son, a son he claimed he was incapable of fathering.
When Logan and Falacci confront Eli with the discrepancy, he continues to claim his innocence, and denies fatherhood. Falacci then theorizes that the doctor may have been a sperm donor in med school. His Ivy League credentials would have earned him a premium in the donor world. When the detectives interview an old med school buddy of Eli's, his ruse is revealed: Eli moves from one beautiful woman to another, and when the girl gets too close, Eli claims he's sterile. Logan and Falacci pull up Eli's donor profile and realize that his sperm is a popular commodity. Stonewalled by the sperm bank's confidentiality agreements, the detectives turn to the same resource children who can't locate their parents use: online message boards. Logan and Falacci meet with a group of children whose mothers all picked Eli's profile. It is soon revealed that someone has been asking these children to send blood samples to a DNA lab. Wanting and hoping for the best, these children are convinced that their biological father is out there looking for them.
However, when it turns out the blood samples have been sent to the research lab where genetics counselor Tom works, Logan and Falacci begin to unravel the mystery. Tom, now missing, has been earnestly searching for his real father in order to get him to donate bone marrow for a transplant to save the life of his dying brother, Ralph. In his own bit of sleuth work, Tom has discovered that Eli is not only the father of both of them, his marrow is a perfect match for Ralph's. The detectives embark on a plan to get Eli, Ralph and Tom all in the same room. Sensing that Tom has some information on the murder, Logan and Falacci arrange for Ralph to call for a 'family meeting'. But when some surprising information is revealed to the detectives, they realize that a bone marrow donation is the only thing that stands between themselves and a confession of murder. Hoping to get Tom to admit to the murder, Logan and Falacci manage to convince Eli into doing some fathering of his own, for the first time in his life.