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.

San Jose, California, 1906. Isolated in her labyrinthine mansion, eccentric firearm heiress Sarah Winchester believes that she is being haunted by the souls of those killed by the guns manufactured by her company.