After a long hard day at work, Catherine Willows heads out to a local bar, the Highball, for a little relaxation. Here she meets a handsome stranger and begins flirting with him. She gets ready to leave, he writes his number on a matchbook for her and walks her out to her car. But when she resists going further than kissing, he becomes angry with her and pushes her into her car door. She pushes him away and leaves, going home to sleep. Later she woken by a phone call from Grissom and leaves her daughter in the care of her mother.
When Catherine arrives at the scene, Grissom and Detective Vartann are standing over the body of Alice Granger; she is lying dead by her apartment building, her face covered by a coat, no purse or car in sight. David Phillips determines that she was killed by a single gunshot wound to the head. Catherine is shocked when Alice's car is found at the Highball, the very establishment Catherine left hours before. Catherine finds a .22 Beretta in the car before going into the bar with Vartann to ask the bartender about Alice. He confirms that he called Alice a cab when she was too drunk to drive home, and makes no mention of seeing Catherine in the bar earlier. At the morgue, Dr. Robbins pulls the bullet from Alice's head wound and hands it to Grissom, who notes that it's from a .25 caliber gun, not a .22. Robbins also notes that Alice was hit at close range, and points out scrapes on her knees that indicate she was probably kneeling when she was shot.
Elsewhere in the lab, Catherine goes over Alice's clothes and finds something on her jacket, which she sends to be analyzed. Hodges has identified the substance on Alice's clothes as metals from automotive sheet metal. Alice did work at a car dealership. Greg identifies the murder weapon as a .25 Winchester, confirming that the gun in Alice's car is not the murder weapon. The gun in the car is registered to her brother Douglas, who tells the CSIs he gave his sister the gun after her ex-boyfriend, Jeff Simon, began stalking her.
Catherine and Vartann question Jeff at the auto workshop where he works. He claims he hasn't seen Alice since she got a restraining order against him. They ask to see his truck, and he complies, Catherine finds a laptop computer with a GPS unit on it in his truck. When Grissom finds a tracker on Alice's car, Jeff is arrested. Thee investigation leads them to a slight, sleazy, dark-haired and wearing a leather jacket--just like the man Catherine flirted with. Mia has run the DNA from the case, but it has become contaminated with DNA from another case. Greg tells Catherine Jeff's alibi checked out; he was indeed pulled over that night. Sara tells Catherine that the man who wrote the phone number on the matchbook has been located and is on his way in.
Sure enough, the suspect turns out to be the man Catherine kissed in the parking lot, a lawyer named Adam Novak. Grissom and Vartann question him, and he admits to buying Alice a drink after he bought a redhead a drink, and as soon as he spots Catherine, he identifies her as the redhead. While Novak recounts his night at the bar, Grissom and Catherine watch from behind the glass. When Grissom asks her about the bruise on her face, Catherine tells him it was an accident. In the interrogation room, Novak stands by his innocence and leaves to get a lawyer. Catherine details her encounter with Novak for Ecklie.
Warrick calls Catherine out on another case. Thirty-one-year-old Holly Pearson has been found dead near her house, a jacket over her face. Like Alice, she, too, was killed by a single gunshot wound to the head. Catherine sees two sets of shoe prints and a courthouse keycard for the parking garage. In the morgue, Dr. Robbins tells Catherine that Holly was killed by a .25 caliber bullet, just as Alice was. He also found some surface tissue from a human tongue in her stomach. Nick confirms that the bullets are on the same gun, and Warrick traces the keycard to Adam Novak.
Catherine is stunned when she returns home and finds Adam Novak talking to her mother and Lindsey. She dials 911 on her cell and leaves it in her car, she confronts Novak. She sends her mother and her daughter inside. He moves toward Catherine, she pulls her gun on him. The police pull up as he swears at her. Novak is arrested. Grissom photographs Novak's tongue and notices a discoloration on the top of it. With his lawyer present, Novak tells Grissom that he drove Alice home, had sex with her in his car, and she was alive when he left. Grissom asks about his keycard to the courthouse, and Adam swears it's still in his car. Nick finds no sign of the keycard in Novak's car, but he does find evidence that it's been broken into.
The prints on the door that was broken into match Jeff Simon, Alice's ex-boyfriend. Catherine lays out the case: Jeff got angry when he followed Alice and caught her having sex in her car with Adam and killed her after Adam pulled away. The next night, Jeff saw Adam at the Highball hitting on Holly and came up with a plan. He broke into Adam's car and stole his keycard, then followed Holly home and killed her, leaving the keycard behind to frame Adam. Grissom asks Mia about the control: turns out someone at the factory contaminated the sterile eqipment. Afterwards, Catherine defends her encounter with Novak to Grissom, saying she just went out after work for a little human contact. Grissom counters that this is why he doesn't go out.