Four victims are found massacred in a New York City hotel and the main suspect, who is found wielding an axe on the streets of New York, is a bright young man and friend to the two male victims. They were partying that night to celebrate the suspect's 21st birthday. Mac and the team find the suspect is high on LSD and can't remember enough to explain the details of what happened in the hotel room. Using blood spatter patterns and fragments of the suspects memory, our CSIs must retrace the men's steps from the night of the murder. The two female victims turn out to have worked for a local drug dealer but decided they wanted out of the business. The girls randomly met up with the young men on the street and accompanied them to a local bar where the girls spiked their drinks with LSD in order to rob them later on that night. The dealer followed the group back to their hotel and with his bodyguard in toe, he exacted his revenge by hacking the girls and the two young men to death with an axe. The young suspect was spared, having been in the bathroom, hallucinating on LSD with the door closed at the time. When he came out, seeing the horrifying scene caused a mental break and he ran out to the streets with the axe. The dealer targets the young student, since he is the last remaining witness, but Mac intervenes and takes down the suspects, saving the young man's life.