Fahrenheit 451

From the text:

Montag grinned the fierce grin of all men singed and driven back by flame. He knew that when he returned to the firehouse, he might wink at himself, a minstrel man, burnt-corked, in the mirror. Later, going to sleep, he would feel the fiery smile still gripped by his face muscles, in the dark. It never went away, that. smile, it never ever went away, as long as he remembered.