he looked up at mack , the man 's mouth still moving , that freight train closing in with a vengeance of noise , its rhythm in lockstep with the brutal pounding in his head , and he could n't take his eyes off mack 's mouth , the old man 's teeth-his synapses sparking , trying to connect , and the noise , god , the noise , and the throbbing- he did n't feel his knees give out .