Edge of Temptation

Walker, Titan's newest recruit, has been sent to rescue Nadine Kincaid,
DARPA's scientist working on a special state-of-the-art exoskeleton for
COS Command's Super Soldier Spy Project. Instead, the kidnapped Nadine
turned out to be Nadia, Nadine's twin sister, who has been protecting
her sister all along. Nadia is perfectly capable of taking care of
herself and Walker's sudden appearance just added more fun to her
adventure. Stuck together, the two of them now have to work together to
keep the newest exoskeleton blueprints out of the enemy's hands. Get
ready for a wild ride!