Guy Montag was a "fireman" whose work was to burn any books found by the authorities, for books are forbidden. The presence or existence of books are illegal so as not to propagate or allow the spread of ideas or concepts from intellectually induced people. This is a symbol of dystopian society's attempt to stop people from having their own rational thinking.
Mildred is the wife of Montag in Ray Bradbury's <em>Farenheit 451</em>, who also seems to support the government's concepts about the destruction of books. So, when she felt the book under her husband's pillow, she asked what that was. But before she could really get the attention of Captain Beatty, her discovery was scolded by Montag, and told to stop snooping and sit down while he was having a conversation with his captain.
