What if, in the course of your everyday life, you walked through an ordinary-looking door and discovered yourself inside a strange tower that stands outside of this world: a tower full of doors, each leading to a different world? From that tower, you could travel anywhere, meet anyone, and do nearly anything. The price of admission, however, is your life. Once you join the Center, you can never go back to the life you once knew. Meet the five newest Center recruits: team captain Ronin, a genetically-modified teenage soldier; team vice-captain Calypso Makkarios, orphaned by the very organization that later recruited her; senior student Truman, whose only home is the Center tower; Damek, the gentle giant whose family left him for dead; and Jinx, an outcaste girl with uncanny instincts. These five must come together as a team to carry out dangerous training missions meant to prepare them for a life as Center operatives. Some are destined to become diplomats or spies, while others will become medics or soldiers-but first they must survive their education.