From the moment she first met him, Callie knew that Simon Montague was a dead man walking. From rock-climbing to wing-suiting, the infuriatingly charismatic tech CEO lives every moment of his life like it might be his last--and given his packed schedule of adrenaline-fueled adventures, Callie calculated that statistically, one would be soon enough. In order to secure funding for her groundbreaking work in astrophysics, Callie must work with Simon--and as much as she tries to resist it, the shy and play-it-safe scientist soon finds herself warming to his outgoing personality and thirst for life--the kind she had long since buried away. But when the promise of a kiss is interrupted by Callie witnessing Simon literally flicker from existence, even her logical, rational mind struggles to find a scientific explanation. She learns that a supernatural phenomenon is threatening to tear Simon from reality itself--and only by facing her own dark and traumatic past can Callie learn what she needs to save the life of the man she's reluctantly developed feelings for.