Christopher gets off of the train and sees how big and noisy and packed the room is.
Christopher had to kneel down on the ground because he felt like he was about to fall over. He had to cover his ears to cope with the loud noises and the size of the room. He worked out, in his mind, which direction to walk in.
He manages to stand up and he imagines a red line that directs him in the direction he wants to go in
A policeman confronts Christopher and tells him that the police were looking for him. When he told Christopher to stay put, Christopher walked away.
Christopher notices some signs on the wall and looks for signs that will tell him where he is going.
He sees too much information at once from all of the signs and the loud noise, so he get's overstimulated.