Last week, Mac and the CSI team discover that the puzzles they have been receiving are all connected to Macâ€™s life and the 333 stalker. While Mac stayed in Chicago to get some answers, Stella, Danny and Lindsay were back in New York trying to examine a crime scene at the subway where a train operator was found dead. While Flack and the CSIs were inside, the train moved, leaving Danny behind.
Danny runs to shut down the control on the rails manually. Just as the train was about to hit another train in the next station, Danny stopped the train by destroying the controls, which turns out to be an mp3 player. The train stopped at exactly 33rd street, using door #3. With the numbers 333, Stella puts two and two together that this is no coincidence and that Macâ€™s stalker may be after them or Mac. She calls Mac to see if heâ€™s okay.
In Chicago, Mac walks through the Tribune building to find a dead man hung from the roof with letters on the wall that looked like a hangman game. With six blanks below the letters, Mac deciphers the puzzle by finding all the missing letters (A-C-D-O-R-W) and jumbled the letters to see the word: Coward. Since Chicago is not his jurisdiction, Mac explained to the Chicago detective how he ended up in the abandoned Tribune building to find a dead body.
Back in New York, the team is busy examining the operatorâ€™s body, clothes and evidences found at the train. Lindsay discovers that the clothing had an anthrax. News spreading quickly, the chief visits the CSI office and tells Stella to get Mac back in New York. Danny examines the mp3 player for prints, but found no match. Zach explains that the mp3 was hooked up at the subwayâ€™s external control, infecting the entire subway system.
Autopsy reports from the body found at the Chicago Tribune showed that the victim was 30 years old, male and was dead from a gun shot to the stomach, buried and dug up only to be hanged again. Mac believes he knows who did it and visits a friend named Jimmy.
The guy found dead was a gangster named Bobby Tool. Mac thinks that somebody put his body in that building to find Mac. The t-shirt that Mac received inside the wrong luggage from Europe was that of Will (Jimmyâ€™s brother who was beaten to death by Bobby Tool when Mac and the others were young). Since Will worked in the Tribune as a paperboy, Mac derives a conclusion and accuses Jimmy of stalking him. However, Jimmy gets mad at Mac for bringing his brotherâ€™s death up and accusing him of something he did not do. As Jimmy left, Mac picks up his cigarette butt to trace Jimmyâ€™s DNA and Flack appears in Chicago as Chief Sinclairâ€™s orders.
DNA prints from the crime scene in New York and with the puzzle pieces are an exact match. However, the killer has no criminal records, so they have no way of tracing him down. Â
Mac tells Flack all about Jimmy, Will and the young version of Mac. When they were about ten to twelve years old, they were working as delivery boys of Sal Marchedy. Since Will was the oldest of the three, he was the one beaten to death when they delivered money that wasnâ€™t what Bobby Tool expected. Throughout the beating and screaming, Toolâ€™s gun slipped across Macâ€™s feet but he couldnâ€™t pull the trigger. Will died on the emergency room, Jimmy and Will never talked about that night ever again.
Jimmyâ€™s DNA was not a match from the puzzle pieces. However, Mac thought about Jimmyâ€™s youngest brother, Andy, whom he thought had no idea of his brotherâ€™s death. As it turns out, Drew Bredford was Andrew (or little Andy who followed them deliver to Bobby Tool and saw his brother die) and Mac quickly returns to New York. Stella also figured this out when she discovers that the negative pieces from the New York puzzle were covered with green xâ€™s, while negative pieces from the Chicago puzzle was covered with blue xâ€™s. The piece she got at Drewâ€™s apartment had blue xâ€™s, which should have been green xâ€™s because they havenâ€™t even had the Chicago puzzle when she went back to check the missing pieces at Drewâ€™s. Â
Stella brought all gifts that Drew sent her the past weeks to find a connection. The prints from the mp3 player are an exact match with Drewâ€™s fingerprints. When Mac and the team was about to enter Drewâ€™s apartment, Chief Sinclair tries to stop them, but Mac talked him into ending this 333 thing and eventually ended up going along with them for the bust.
While Flack, Stella and the others were looking for Drew, Mac is down at the wine cellar. Drew injected Mac with drugs at the back of his neck and got abducted. In the middle of a dozen light rays, Mac is trapped and anyone going into the door to save him or with just one move from Mac will trigger the guns to shoot.Â
Drew has given all the clues with the puzzle and the crime scene. The entire CSI team worked to find Mac and they discover that the mp3 player had one song uploaded to it â€“ â€œTrain to Nowhereâ€, the 6th track on SVâ€™s album. This led them to Macâ€™s location.
Drew is pissed that Mac is being cheered as a hero in the newspapers when he led a drug bust. He says â€œthe thing about heroes is that sooner or later, someone will know the truthâ€. As it turns out, Andy followed Mac, Jimmy and Will to Bobby Toolâ€™s room (Room 333), where he saw how his brother died. Andy blames Mac for being a coward and not shooting Tool down when his brother is being beaten to death. Mac explains that he was just a kid then. Â
Jimmy calls Drew to save him from making a big mistake. As soon as Jimmy entered the room, he was shot by Andyâ€™s trap. Mac then triggered one of the lights to shoot Andyâ€™s arm. Flack says that during those kinds of situations, it was â€œshoot to killâ€. Mac explains that the family had already lost enough.