Eager to escape a painful past, Michelle Harper joined the Off-Earth Special Operations Service (OE SOS) in hopes of becoming someone other than herself.

Taking the name Cathis, after the Consolidated Armaments Technologies Human Interface Soldier program for which she volunteered, she underwent genetic and physical alterations to become one of Earth's most powerful and terrifying warriors. However, an unexpected visit to Earth results in conflict with her estranged sister, Kayla, when she challenges Cathis' path and who it has driven her to become.

But everything changes when Cathis learns of a dark secret that puts not only her life in danger, but Kayla's as well.