Wolff told 'Real Time' host Bill Maher that he was "absolutely sure of" Trump being involved with a woman in the White House but that he didn't have the "ultimate proof."

Michael Wolff just gave President Donald Trump another reason to send angry late-evening tweets about his incendiary new book: In a new interview, the author of Fire and Fury: Inside the Trump White House suggested that Trump may be having an extramarital affair while in the White House.

When asked whether there is a section in Fire and Fury that he wonders that the press isn't asking about, Wolff told host Bill Maher on Friday's installment of HBO's Real Time that there is, "but I can't tell you what it is."

"There is something in the book that I was absolutely sure of, but it was so incendiary that I just didn't have the ultimate proof," he said.

Maher then pressed Wolff on what the topic of the incendiary revelation is, asking whether it is a "woman thing."

"Well, I didn't have the blue dress," Wolf responded, referring to evidence in the Monica Lewinsky scandal with former President Bill Clinton, before telling Maher that "it is" about a woman.

"It's somebody he's fucking now," Maher said.

"It is. You just have to read between the lines," Wolff said, "It's toward the end of the book." After being pressed some more by Maher to reveal details about where the suggestion of an affair is, Wolff said, "You'll know it. Now that I've told you, when you hit that paragraph, you'll say 'Bingo.'"

Last week, The Wall Street Journal reported that Trump's personal lawyer had arranged a $130,000 payout to adult film actress Stormy Daniels before the November 2016 election. The Journal reported that she privately alleged to having had a brief sexual encounter with Trump in 2006, after he had had his first child with wife Melania.

Wolff's controversial book is also coming to television, The Hollywood Reporter learned on Wednesday.

Endeavor Content has purchased television and film rights to the book. Wolff will executive produce the series, with veteran Channel 4 and BBC executive Michael Jackson also on board to produce. A network is not yet attached.