Outside the secret military base where Em is imprisoned, war rages. The world has been coming apart at the seams ever since the U.S. government cracked the code of time travel and built a machine to weaponize time. The only chance Em and the body in the cell next door have to change this terrible present is to escape to the past and stop the man who created the machine. Four years earlier, the biggest problem in Marina's life is figuring out how to tell her shy and brilliant best friend James that she's in love with him. That is, until he night an assassin's bullet changes everything and sends Marina and James on a desperate hunt for answers, with a killer who seems to anticipate their every move right on their heels. Marina will protect James at any cost. Em will sacrifice everything to rewrite her future. Only one of them can succeed.