Sara's in Trace, talking to Vincent, a nicely snide lab tech who informs her that he has exactly three minutes and five seconds for her. She's good with time management, so that's fine with her. Vincent comments, "I heard Sanders broke out of here, fared poorly, and disgraced us all." Okay -- like Liam or no, that was really funny, especially with the twin ideas that a) the lab techs are like housecats looking for any opportunity to escape, and b) there's some sort of lab tech cabal that's waiting to lynch Liam for besmirching their rep. Sara quickly corrects that misperception; Vincent looks up, surprised. Then, mindful that the clock is ticking, Sara gets to the point; she found chloroform, and she needs to know how it got on the inside of a tire. Vincent asks, "You ever hear the expression 'pissing up a rope'?" "Not in a scientific context, no," Sara replies. The tech clarifies: "I don't know if you can urinate up a rope, but you can urinate against a rope, and the urine will dribble down. Answer your question?" It does.
In the garage where they've set up the bus, Warrick is bending over the right front tire and telling Gil, "You know we're going to have to document this for The Journal of Forensic Science, right?" Warrick, Sara, and Gil set up the experiment: a tire with the same maintenance record as the one that blew, some chloroform (introduced into the tire by means of a glass stirring rod), and then, time to start the bus and see what happens. Warrick and Gil watch Sara do this, impressed by a woman who knows her way around a tire gauge, and they both notice that Sara used her left hand to stay steady while sabotaging the tire. Sara runs off to fingerprint the right rim of the tire to see if they can nail the perp.
Time has presumably elapsed. Sara's dusted and found a match for Sean Nolan; Gil and Warrick are bus-sitting and playing a game of chess. Warrick's cell phone rings, and he tells Gil, "Sara. She's at the print lab. She needs me." This last sentence is delivered in an almost-teasing manner -- is Warrick tweaking Gil? -- and as Warrick gets up to go satisfy Sara's need, he checkmates Gil. Gil hunches over the board, wondering, "Has the pupil become the master?"
Sara's all giddy because the print matches former bus driver Sean Nolan. Meanwhile, Nicky and Gil are figuring out that the tire should blow at any moment; Sara and Catherine come by for the show. The tire blows right on schedule, and Gil decrees that this confirms the sabotage-in-Barstow theory. Catherine cuts the celebration short by pointing out that this in no way implicates Eric, as his car came up chloroform-free.