The Ninth — Christopher Cartwright

U.S. Navy SEAL team's Omega unit sat making last minute checks on their weapons and equipment. Their mission: to hold the uppermost level of an ancient stronghold that had shown little military significance – until now. Each man knew what was required of him; they had gone over the drills more than thirty times. The 8-man team had been together for years, and the were a tightknit, perfectly functioning unit. Then, there was the ninth man, the only one who didn't belong.