Omitting information is a form of lying. As the oath people say before testifying in court indicates, telling the truth means telling the "whole truth" and not withholding important information.
Beatty receives information about an "alarm-report," alerting the firemen to a house that has books. Beatty takes the address that comes across the telephone, looks at it, and shoves it in his pocket. Even though he only glances at the paper quickly, he knows it is Montag's address. He says, for instance, "This is a special case" as the firemen are leaving. He also drives the Salamander, which he never does. However, he doesn't tell Montag that it is his house they are headed toward.
Instead, he lets Montag experience the shock of realization when they arrive. Beatty seems to take a sadistic pleasure in doing so, because as they pull up, Beatty taunts Montag:
Beatty was watching his face. "Something the matter, Montag?"
As Beatty's conversation with Montag shows, he has known for awhile that Montag...
(The entire section contains 3 answers and 611 words.)