In the ninth episode of "NCIS" Season 4, titled "Twisted Sister," daughter of series producer Donald Bellisario and stepsister of Sean Murray, Troian Bellisario, stars as Timothy McGee's hot-headed sibling, Sarah, in her final appearance on the program to date. The episode opens with Sarah arriving at her older brother's apartment, and it doesn't take long to figure out that something's terribly wrong. She's dazed, disheveled, and covered in blood, dropping a bombshell right out of the gate: "I think I killed someone, Tim."
As anyone would be, Tim's taken aback by this revelation, but he doesn't allow his emotions to get the best of him. Instead, Tim chooses to let her in so she can wash off the "mystery blood" and get some much-needed rest. In the morning, he makes the bold move of calling out of work sick so he can attempt to solve the case without the help of the NCIS team. However, when he visits her college and realizes his colleagues are investigating a dead sailor on campus, he promptly flees the scene.
Though he was certain that sticking his neck out for his sister was the right call, McGee soon came to realize that his career-threatening choices couldn't remain a secret forever.
