The Osterman Weekend
by Robert Ludlum
John Tanner, Director of News of a US TV network, is convinced by a CIA agent that the friends he has invited to a weekend in the country are engaged in a conspiracy, called Omega, that threatens national security. But then everything John Tanner thinks he knows about his closest friends is overturned, and he is set against them. But when Omega finally reveals itself, he realizes that he has been manipulated from the very start.