It was a clear spring day, just a hundred years after the birth of Christ, when Jerry Pierce wandered into the Roman Colosseum to spend a quiet afternoon watching gladiators fight to the death. Sixty men had been killed already, not including the 15 condemned criminals executed at lunchtime, when an explosion rocked the arena. Bodies flew from the broad terrace just above the arena where the emperor had been presiding over the event. Shrapnel sliced...