Tracy was serving as a surrogate mother for Linda and Jim Tolliver, but unbeknownst to all parties involved, Randi had donated her egg and mixed it with Jim's sperm to create the baby. This was done after Randi's attempts to have her own child with Jim's donated sperm failed, with the attempts prompting her to plan to take the Tollivers' baby as her own. In the beginning of the episode, Randi chased after Tracy and stabbed her to death, but was run off before she could slit her throat. The baby--a boy--survives and is born; all the while, the evil Randi continued her murderous spree, while also wearing padding around her waist to fake her pregnancy.
After killing Dr. Hanson and another nurse, Randi appeared to Dr. Maura Isles at the hospital, planning to take the baby. At that moment, Jane Rizzoli (who had figured out Randi's plans) arrived and told Maura to keep an eye on the baby, and following this, Randi threatened both women with a scalpel and demanded the baby. Jane revealed Randi's entire scheme, with Randi ranting that she was the baby's mother and she even considered paying Tracy for him. Jane later brandished her gun and ordered the psychotic villainess to drop the scalpel, which she does; after which Randi is handcuffed and arrested by Jane.