The team lands the case of a young girl, Kira, pushed from her dorm window. When a connection to an old case comes up, Sara grabs the chance to put away the man she believes is a killer: Marlon West. His sister Hannah publicly confessed to a prior murder, but secretly told Sara that her brother Marlon was the real culprit. Now Sara wants to put the guy, a student at the university, away for good. But 14-year-old Hannah is on the scene too, a student at the graduate school where her brother attends college. Sara is certain Hannah is manipulating the situation.
A broken tooth from the scene ties Marlon to Kira, since it appears that Kira punched him and embedded a tooth in her hand. But she slept with another young man that night, and they were both high on GHB. It turns out that their sexual lubricant was spiked, and Marlon's fingerprint was on the tube. Everything leads to Marlon, but Sara is convinced that Hannah is the guilty one. She believes Hannah wanted to get rid of Kira to have her brother all to herself. Marlon confesses to Sara that he had Hannah help him spike the lubricant, but he wouldn't have hurt Kira. Sara believes him. They try to get Hannah to confess to Marlon privately, but she knows immediately that he's wearing a wire. Not long after, seeing no end in sight, Marlon hangs himself in his jail cell. Hannah is devastated, but Sara finds no pleasure in seeing the girl suffer.
Sara has ghosts to bury, and she's come to the realization that she must leave to do so. At the lab, she kisses Grissom goodbye and places her vest in Ronnie's locker. Before she goes, she leaves Grissom a letter that explains her decision, closing it with the words, "Know that you are my one and only. I will miss you with every beat of my heart... I love you. I always will. Goodbye."