Into the aftermath of his confrontation with Tulp had walked Jan Spaen. Yet despite the experience they’d shared, they didn’t meet again until after Huygens’s life had totally changed.

The Tulp incident had shocked him to his senses. Dreading the arrival of the police, he’d hidden in his rooms, physically ill with fear and guilt, and expecting some sort of demand from Spaen. But when weeks passed and nothing happened, he dared to believe he’d escaped punishment. He had another chance.

He’d spent the next twenty years atoning for his sin. Dropping his gang, he quit drinking, studied hard, and graduated first in his class. He won a coveted professorship at Leyden University; he also taught in Rome and Paris. At his private clinic, he treated both prominent citizens and charity patients. He married Judith, the rich girl his father had chosen for him, and fell in love with her. As time went on, Huygens gave less and less thought to his past evil, or the man who’d colluded in it.

Then, while attending a medical conference in Amsterdam, Huygens had left the lecture hall one evening with a group of colleagues, and spied, standing in the vestibule, a ghost from the past. Shock burst like a geyser of cold, foul water in Huygens’s chest. He stopped dead in his tracks.

Jan Spaen smiled. “That was a brilliant lecture you just gave, Dr. Nicolaes Huygens,” he said.

His features were still handsome, his body strong, his hair still golden, his gaze bold and knowing. Huygens would have recognized him anywhere. Now he was horrified to hear Spaen’s use of his name and title: Though Spaen hadn’t known his identity on that long-ago day, he did now. And Huygens realized that Spaen had at last come to collect on his debt.

“After all this time, we have much to talk about.” Spaen led Huygens outside to a deserted street. “I’m a trader with the East India Company, in town until my ship sails again. I could use a good medical man on my staff. From your lecture, I know you’re an expert on traumatic injuries and tropical diseases. How about it?”

An awful rushing sensation came over Huygens, as if an invisible tide were receding from him, taking along everything and everyone he cared about. “But I can’t go to sea,” he protested. “My work; my family …”

“The Gertje sails for the Spice Islands next week,” Spaen said. “I’ll see you then.”