When a mounted police man, Officer Valasquez, is shot by a sniper, Mac discovers the bullet is lodged in his horse. Mac faces the dilemma that 'following the evidence' will destroy the animal. Danny uses facial recognition software on surveillance footage during the shooting to identify bag vendor, Willie Chancey, on a disposable cell phone, appearing to communicate with the sniper. The CSI's find the cell phone at the scene and Det. Flack traces the call to airplane passenger Jerald Brown, who is detained before take off. Mac makes a 3-D replica of the bullet, allowing the horse owner's daughter to say goodbye to the horse before the extraction operation, which the horse survives. Det. Flack finds Willie's car in the airport parking lot, with Willie shot dead in the trunk. The dials inside the car are on full blast, leading Stella and Danny to discover they trigger a floor plate trap for a secret compartment housing the rifle used to kill Officer Valasquez. The CSI's find Jerald's fingerprints on the rifle, and Jerald confesses working with Willie to shoot the first officer 'that came along'. Jerald wanted to get even with the cops for wrongly accusing his father of drug possession and sending him to jail where he was killed. Aiden investigates the murder of teenager Lenny Starks, inside a pizzeria used as a front for an illegal sports book. Despite being strong armed by the pizzeria owner, Aiden tracks a burn mark on Lenny's face to the pizza oven, and finds fingerprints on the oven bar matching a female employee and the owner. When Lenny came up short on a payment, the owner, with the help of the pizza girl, slammed Lenny's head in the oven, causing him to later die from the blow.