As revealed later on, the valves were defective, resulting in numerous deaths, with two of them being in Boston. Rory's partner, Steve Sanner, found out about the defects and planned to blow the whistle, which would cost the company millions as CNS was planning to buy them out. While Rory relied on Steve to keep quiet, Kate decided to take matters into her own hands.
As shown in the beginning of the episode, Kate was in her basement preparing a homemade silencer, and planned to kill Steve during their high school reunion, which Jane Rizzoli attended with Maura Isles (doing so due to Maura never experiencing attending a co-ed school). The duo encountered the Grahams at the reunion, with Jane referring to Kate as the queen of the mean girls to Maura. Later on, Kate followed Steve to the school's football field (where Steve was reliving his playing days) and fired her makeshift weapon at Steve, killing him instantly. After finding out that fellow school mate Debbie Tibbet knew about Steve's plan, the evil Kate murdered Debbie as well, strangling her with a rope and making it appear that she committed suicide. The villainess also sent a threatening letter to Steve's wife, Emily, threatening to kill her and her kids unless she kept quiet.
After another school mate, Maria Korkman, died due to the valve, Jane had Barry Frost look into the valves, and it was there that the defections were revealed along with the company being sold to CNS. With that, Rory was suspected in the killings, but when they went to the Graham home to confront Rory, Jane realized that Kate was the true killer, as residue from the football field was found on her shoes. Kate was in the bathroom attempting to get rid of Steve's files, which had proof of the defective files, but she was arrested by Jane, while Frost discovered the drives. Kate later admitted to the murders, stating that she had to do something because Rory (who was also arrested for the faulty valves) wouldn't.
- Erin Daniels later appeared on Stalker as psychotic villainess Candace Donovan.
- "You weren't going to take care of it. You didn't even bother to look at your stupid football bro's laptop until I showed you! 'Oh boo hoo, we're making broken valves, why don't we all cry about it like little girls and take down the company?'" (Kate Graham's bold admission to the murders, while chastising Rory)