When Ethan and his team attempt to sneak into the CIA's Langley headquarters in order to steal the Non-official cover (NOC) list, the room in which the list is stored is heavily protected by a number of security measures. Just one of these checks is a weighted floor, meaning that Ethan has to be lowered into the room via a cable, and steal the list without any part of his body ever touching the floor. He is held in place by the psychopathic Krieger (Jean Reno). Things get further complicated, however, when a rat appears in the vent where Krieger is, causing him to lose focus on the task at hand and appear to bludgeon the animal to death. This causes him to let go of the cable temporarily, and as Ethan heads towards the weighted floor, Krieger only barely grabs the cable in time to prevent the plan from failing disastrously. Also, the rat's a not-so-subtle visual signifier that Krieger isn't to be trusted, because he's exactly that: a traitorous rat.