The answer to this question can be found in the section entitled "The Sieve and the Sand." As Montag comes back, he is understandably very nervous. He brings with him the book that he illegally took from the woman's stash of books and also Faber's voice in his ear. It is necessary for Faber to reassure him and to try and calm him down as he reenters the firehouse. As Beatty sees him, note what he says to the men around him with whom he is playing cards:
"Well," he said to the men playing cards, "here comes a very strange beast which in all tongues is called a fool."
Beatty clearly makes fun of Montag and of his position, and awaits the delivery of the book with his palm facing the ceiling. After Montag has given him the book, and Beatty throws it away, Montag joins Beatty and the men for a game of cards, but Beatty uses this as an opportunity to continue to lecture Montag on the dangers of books. It is clear that although Montag has returned the book, the conflict is not over.