All for One

David Sutton (Chris Tallman), a high school driver's education/science teacher, is killed by a hit-and-run driver. The car used is from his own class. A fiber from what is believed to be from a friendship bracelet is found inside. When Samantha Cole (Alexis Raich), Sutton's chemistry student, attempts a drug overdose before his death, her background is checked. The team learns she had a tightly knit circle of friends and that Sutton was exchanging grades for sex. Sutton also tried to ruin Cole's reputation before she could report him. One of her friends had tried to entrap him but was discovered and fled. Sutton pursued them and was hit. Each friend confessed to it and no evidence could single out a viable suspect, so all are set free. Meanwhile, although Jane remains in contact with Casey, she gets asked out on a date by Detective Martinez (Amaury Nolasco). Maura calls it "chemistry", but Jane says it can never happen.