The Osterman Weekend by Robert Ludlum

A television journalist is warned by an intelligence operative that his closest friends may be part of a foreign spy network and is coerced into hosting a weekend gathering to help expose them. As covert surveillance, manipulations, and staged provocations spiral out of control, paranoia fractures long-standing friendships and violence erupts. He ultimately uncovers a deeper conspiracy that has been using him as a pawn, forcing a reckoning with betrayal, truth, and the catastrophic costs of clandestine power games.