Capital Crimes — Lawrence Sanders

He calls himself Brother Kristos, a bearded bear of a man, whose eyes can pierce the soul. His origins are cloaked in mystery, but his present mission is clear: to take upon himself transgressions of the wives of Washington, absolving them of guilt.
To those who have been purged by Kristo's message of unending love and the death of sin, he is a messiah. To the President of the United States, he is a miracle worker - the only person who can heal his son when state-of-the-art medicine has failed. But to John Tollinger, executive assistant to the White House chief of staff, Kristos is a lecherous apostate, a vodka-guzzling womanizer whose political influence over a new and emotionally unstable president is fast becoming a stranglehold.
Under order form his boss to get the goods on Kristos, Tollinger comes closer than he'd like to the mad monk who's become the darling of the capital. Tollinger is a worldly, cynic, while Kristos is a holy reprobate, yet Tollinger begins to see a horrifying bond emerge between them.
Chained together by the workings of a violent, inexorable destiny, they will confront each other in a place where good and evil whirl in a storm of retribution - from which there is no way out...