CSI: NY Season 1 Episode 20 : Supply and Demand

When a college student is beaten, shot to death and his apartment ransacked in what appears to be a drug-related hit, the team must track down his killers. After examining the evidence in the murdered student's apartment, the team finds traces of pure, unprocessed heroin and discovers that the victim had a female roomate who is now missing. Meanwhile, Stella's aggressive interrogation tactics with a witness threaten her police badge.