After Ethan gets the NOC List, he needs to meet with Max and the mole so they can catch the mole (Jim Phelps). This second meeting with Max happens on a high-speed train that is to cross the English Channel. The train provides three scenes that are really the climax of the movie.
The first scene has Ethan providing the NOC list to Max. Max had paid Ethan for the NOC List and wanted to upload it. Luther uses an electronic jamming device to keep Max from uploading the file before they hit the Chunnel. Given that this was filmed in 1996 and that they were on a moving train, one can imagine how slow the phone line was that Max was trying to use.
The next scene, which is where this clip is from is where it gets really fun. Claire walks into the luggage room on the train and sees Jim. She talks with Jim about how he is the mole and how they will set up Ethan and take the money. At this point, Jim stands up and PULLS OFF A MASK. In reality, she had been talking with Ethan. Ethan had made Claire believe he was Jim with the use of the mask. Then the real Jim walks out from behind another section of the luggage car. Ethan gives her the money and then puts on a pair of glasses with a camera built-in, letting Jim know that Kittridge has seen that he was still alive. Jim then kills Claire and has a quick fight with Ethan before escaping out of the luggage car.