Steven Grant, a mild-mannered British museum gift shop employee, is troubled by relentless sleepwalking and vivid nightmares. He discovers that he shares his body with Marc Spector, a battle-hardened mercenary with dissociative identity disorder. Marc serves as the avatar for Khonshu, the Egyptian moon god, granting him enhanced abilities to enact justice. As their lives intertwine, Steven struggles to comprehend the reality of his dual existence. The characters are dragged into an ancient and mystical conflict involving Egyptian gods and artifacts. They must navigate their tumultuous relationship amidst external threats that challenge both their physical and mental fortitude.

While piecing together his memories and actions, Steven encounters Arthur Harrow, a charismatic yet fanatical leader with intentions of resurrecting the goddess Ammit for global judgment. Caught between his own fractured identity and looming danger from Harrow's cult, Steven desperately seeks the truth about his past and his connection to these supernatural events. He is joined by Layla El-Faouly, an adventurous archeologist with personal ties to Marc’s past. Their shared goal to thwart Harrow’s destructive plans propels them on a frantic journey through ancient myths and peril. As identities merge and confront fate, they confront shadowy betrayals and uncover hidden secrets that drive them towards a destiny that neither fully understands.