Known Force 17 personnel were located and accounted for. Those thought to possess the skills or education necessary to build the bomb that leveled the Rome embassy were singled out for special attention. Arab informants were called in and questioned from Ramallah to Gaza City, from Rome to London. Communications intercepts stretching two years into the past were filtered through the computers and sifted for any reference to a large-scale operation in Europe. Old surveillance and watch reports were reexamined, old airline passenger lists scoured again. Rimona returned to her hangar each morning to search for traces of Rome in the captured files of Arafat’s intelligence services.

Gradually, Room 456C began to resemble the command bunker of a besieged army. There were so many photographs pinned to the walls it seemed their search was being monitored by an Arab mob. The girls from the data rooms took to leaving their deliveries outside in the corridor. Gabriel requisitioned the room next door, along with cots and bedding. He also requested an easel and a chalkboard. Yossi contemptuously pointed out that no one had seen a chalkboard inside King Saul Boulevard in twenty years, and for his impertinence he was ordered to find one. It came the next morning. “I had to call in a lot of favors,” said Yossi. “The stone tablets and carving tools arrive next week.”

Gabriel began each day by posing the same series of questions: Who built the bomb? Who conceived and planned the attack? Who directed the teams? Who secured the safe houses and the transport? Who handled the money? Who was the mastermind? Was there a state sponsor in Damascus or Tehran or Tripoli?

A week into the investigation, none of the questions had been answered. Frustration began to set in. Gabriel instructed them to change their approach. “Sometimes these puzzles are solved by the piece you discover, and sometimes they’re solved by finding the piece that’s missing.” He stood before his chalkboard and wiped it until it was a blank slate. “Start looking for the piece that’s missing.”