Bang, Bang, Your Debt: Horatio and his team investigate the death of college student Jessica Taylor, whose burnt body is found in an SUV, her friend Brandon Fox's unconscious body nearby. Jessica's autopsy reveals that she was killed by carbon monoxide poisoning, not by the fire. In her dorm room, the CSIs discover that Jessica fell prey to credit card solicitors on her college campus and has racked up an enormous debt. Her answering machine messages indicate that the collectors have been coming after her aggressively, threatening to take everything she has if she doesn't pay up. Brandon wakes up from his coma, but yields no further clues.
When a used condom found in Jessica's dorm room is traced back to Keith Reynolds, credit manager at her bank, the CSIs learn that conned her, and many others, into having sex him in exchange for erasing her debt. Out of sheer desperation, Jessica had sex with Reynolds, but he reneged on his end of the deal. Just as Calleigh and Delko confront Reynolds while he's manning his booth on campus, gunfire erupts out of nowhere, killing Reynolds. Ultimately, we learn that Jessica and Brandon, who was also in over his head with credit card debt, made a pact to commit suicide, thinking it the only way to free themselves from all their debt. Jessica was successful, but Brandon wasn't. His anger drove him to sneak out of the hospital and gun down Reynolds for taking advantage of Jessica.
Still recovering from his brain injury, Delko is forced to deal with his hallucinations of Speedle, who died three years ago. Things become even more puzzling when he finds Speedle's credit card in his Hummer and learns that there has been some recent activity on it. Horatio gets involved, and they discover that someone within CSI has been illegally making charges on Speedle's card.