Three gunmen wearing masks take a family of four hostage. They forced a man to open the safe, then shoot three. A pregnant woman jumps out the window and attempts to escape but is cut down. Catherine tries to reach her estranged daughter Lindsey. The mother dies but the unborn baby survives. With Max hospitalized, Catherine is running the scene. Penny is in shock from the gruesome murders. While vomiting, Penny finds balled-up paper in the bushes. The notes Penny found point to an inside job. A distraught Penny tries to quit but Catherine talks her down. One killer tended to the pregnant daughter after she was shot. He is the person who left the bloody handprint Allie found. Catherine lets Penny investigate a crocheted koala that she had vacuumed up. DNA from the handprint and the kaola match. Penny thinks the killer wants to get caught. The shell leads to the man who sold the three shotguns to the killers. Max uses her CPS connections to get the swab that Catherine was refused. The pregnant daughter was a gestational carrier and one of the killers was the infant's biological mother. Another family is executed, along with the female killer. Max notices Catherine is distracted and sends her to see Lindsey. Catherine's lunch with Lindsey goes badly. Penny finds a kaola from the second scene. Justin Einsteen, who was in a photo of the first family, admits he's the father of the infant. The female killer was the sister of the egg donor Lucia. Catherine negotiates with Lucia, who is holding a shotgun on her remaining triplet, Darcy. Darcy had put Lucia's earlier baby up for adoption and was the leader of the killer trio. Catherine wrestles the gun away from Lucia. Lindsey texts "I love you" to Catherine.