It was a little after 9 p.m. when a Palestine Liberation Organization official stepped out of the elevator into the lobby of Paris's Le Meridien Montparnasse, a modern luxury hotel that caters to businessmen and well-heeled tourists. The PLO official was going to dinner with a friend, who was waiting by the front desk. As they pushed out the Meridien's front door, they both noticed a man on a divan looking intently at them. It was odd enough that at dinner they called a contact in the French police. The policeman advised the PLO official to go directly back to the hotel after dinner and stay put. The police would look...