Warrick visits Maddox and learns that Maddox fired Nolan for having pot in his locker. Hmmm. Motive! Warrick gets all the bus maintenance records from Maddox.
Cut to Catherine, Brass, and Warrick in Barstow, having a look around and talking about the futility of finding a saboteur in a rest station. Just then, Warrick rings Grissom, telling him that the fired Nolan has been working in Barstow for two months and -- quelle coincidence -- three of Maddox's buses have had blowouts in that time, all of which have gone through Barstow, and only one of which had the faulty bolt. Gil hangs up and listens as the rumblings of the deus ex machina recede into the distance.
The three CSIs then head over to Nolan, quickly pin him as the suspect -- with a side trip from Gil into the probability of Julius Caesar's breath being all over the world -- and confirm when they use a hand-held detector to pick up traces of chloroform on a tire gauge. Nolan confesses, citing revenge as the motive: "I have one joint on the weekend -- on my time -- and I got jacked as a junkie." Dude, if he responded this way, maybe he needed to smoke a little more to mellow out some. He had figured that even if the tires blew, the suspension system would hold. "There's a first time for everything," Brass quips, and arrests him. Gil and Catherine debate the charges (second-degree murder), concluding that anger (Nolan) and greed (I'm pinning that on the Brillman bolt company, which charged for a doctored product) led to all those deaths. Catherine, Brass, and Gil walk off, and the episode ends with another bus -- presumably one that won't blow up -- pulling in to the rest stop.