The poker game that is played between Montag, Beatty and the other firemen is interrupted by Beatty's words to Montag, that insinuate he knows a lot more about Montag's betrayal and guilt than he will admit at first. Of course, Montag was already feeling very guilty even before he entered the firehouse, as this quote displays:
If Beatty so much as breathed on them, Montag felt that his hands might wither, turn over on their sides, and never be shocked to life again; they would be buried the rest of his life in his coat sleeves, forgotten.
Beatty's argument against books, and the way that he uses a number of quotes to reinforce his argument is of course what interrupts the poker game and makes Montag throw in his hand. However, at the same time, the station bell ringing also interrupts the game, and gives Montag the release of not having to respond to Beatty's taunts.