Dr. Caleb Maddox is a crack San Francisco toxicologist leading a ground-breaking study of the human pain threshold based on minute analysis of chemical markers. He has also just broken up with his artist girlfriend after she discovered a shocking family secret in his past. Seeking solace, Caleb finds a dark, old-fashioned saloon called House of Shields, and is mesmerized when a beautiful woman materializes out of the shadows, dressed like a 1940s movie star. The enigmatic Emmeline shares a pouring of absinthe with him, brushes his arm and vanishes. As he pursues her through the brooding, night-time city, desperate to see her again, he simultaneously becomes entangled in a serial murder investigation that has the police stymied - men gone missing, fished out of the bay, with no clue as to how they met their end - until Caleb's analysis of the chemical markers in their bodies reveals that each one was tortured to death. Also present are some of the key components of absinthe. As Caleb finally looks forward to a night spent alone with Emmeline, part of his mind wonders if behind the seductive vision is something utterly terrifying...