He moved on to dueling in pairs. Luke announced he would be my partner, since this was my first time. "Good luck," one of the campers told me. "Luke's the best swordsman in the last three hundred years." "Maybe he'll go easy on me," I said.

The camper snorted. Luke showed me thrusts and parries and shield blocks the hard way. With every swipe, I got a little more battered and bruised. "Keep your guard up, Percy," he'd say, then whap me in the ribs with the flat of his blade. "No, not that far up!" Whap! "Lunge!" Whap! "Now, back!" Whap! By the time he called a break, I was soaked in sweat.