A brutal mugging leaves Grey Trace paralyzed in the hospital and his beloved wife dead. A billionaire inventor soon offers Trace a cure — an artificial intelligence implant called STEM that will enhance his body. Now able to walk, Grey finds that he also has superhuman strength and agility — skills he uses to seek revenge against the thugs who destroyed his life.

Young, charismatic, and hardworking, Sparra Farrell seems to be sailing into a happy, respectable life. He has a solid job and an adorable fiancée named Paula, and already owns a modest house in the country outside Melbourne. The only odd thing is that Sparra says precious little about his past — but that past is about to catch up with him, and wrest control of his present.