Part 2 of Night marks the transition from the Hungarian ghetto to the concentration camps. Elie and his family are in a cattle car and people around them (at the end of Part 1) are still in denial that anything will happen. They have thought that they will be shipped away so people can loot their homes, or that they were being sent away "for their own good," the front being so near.
Part 2 shatters such illusions. In the cattle car, there's no room for comfort. No one could lie down and only a few could sit at a time. Ventilation is poor and despite the buckets of water they'd been given, they find themselves dealing with intolerable thirst by the end of the second day. Whereas the dalliances of the young would normally be condemned, they are now ignored. The adults present--even the mothers and fathers of the youth in question--are too hungry, thirsty, exhausted, and terrified to say or do anything.
The coldness of the mood is solidified at the Hungarian border, when the doors are opened and they learn that they are now in the custody of the German Army. A German officer tells them: "There are eighty of you in the car. If anyone goes missing, you will all be shot, like dogs" (24). When they'd left their home, one person had been put in charge of each car, and the threat was only to shoot the person in charge if anyone escaped. Now, it would be all of them.