“I still don’t understand what Rattigan wanted with us,” Thomas said, sitting up in bed with a blanket draped around his shoulders and a hot-water bottle steaming by his feet. Miss Fitch had insisted on both of these measures, as if he were dying of pneumonia.

Sam, Pippa, Max, and Mr. Dumfrey were gathered around him. Sam was sitting on his bed, and Thomas couldn’t help noticing that Max had chosen to sit next to him, slightly closer than was necessary. Pippa was sitting cross-legged on the floor. And Mr. Dumfrey was standing, polishing his glasses with his handkerchief. They had just finished telling him everything: their realization that Bill Evans had bribed Potts to steal the head; that he was responsible for the murders of Potts, Anderson, and Weathersby, their visit to his apartment, their discovery of his body, and their encounter with Rattigan. Mr. Dumfrey listened quietly and didn’t even lecture the children about how many rules they had broken. His face was more serious than Thomas had ever seen it.

Finally, when they were finished speaking, he sat down heavily on the end of Thomas’s bed.

“I’m going to tell you a story now,” he said. “I’d been hoping—praying—that you might never have to know. But I see now that it’s time.”

“Know what?” Max said, her dark eyes glittering.

Mr. Dumfrey looked up at the ceiling. “Professor Rattigan was a brilliant biologist—the best, perhaps, who had ever lived. When the war broke out, he enlisted, as so many promising young men did.”

Thomas settled back against his pillows. He didn’t know where the story was going, but he had a sense of something momentous about to be revealed.

“War does things to people. You have to understand. Many men came back broken. Not in their bodies, but here.” Mr. Dumfrey tapped his heart. “And here.” He tapped his head. “Rattigan hated the war. Who wouldn’t? An idea began to form. What if he could make soldiers so perfect, so strong, so smart, that they couldn’t be defeated or killed by ordinary means? We would never have to go to war again. No one would risk it. Eventually, there would be no point in waging war at all.

“His idea grew into an obsession: when the war ended, he would create a team of individuals so extraordinary as to be invincible.”

Thomas tried to swallow and found that he couldn’t.

“During one of the bloodiest battles, almost every single member of his platoon was wiped out. Only Rattigan and two others survived. Rattigan was awarded the Medal of Honor for bravery and discharged.” Mr. Dumfrey closed his eyes. “But he came back from the war different. Obsessed. Convinced that his way was the only way. He wanted to create an army of his own—the most powerful army in the world. To that end, he got hold of four orphaned children, and began his experiments on them.”

Mr. Dumfrey opened his eyes. His gaze traveled slowly over the four of them: Thomas, Sam, Max, and Pippa. Despite the blanket and the heat of the attic, Thomas felt goose bumps pop up all over his arms.

“He was eventually arrested. The children scattered. They were placed in foster homes and orphanages. One of them escaped and spent many years on the street.” Dumfrey’s eyes ticked to Max. “The other three found their way into my care. It was not an accident. I admit I was looking for you—for all of you. I knew you were extraordinary, and I wanted to make sure that Rattigan would never get to you again. Even after Rattigan was locked away, I was scared. I’m still scared.”

There was a long moment of silence. It took Thomas several tries before he could find his voice.

“How?” he croaked out. “How do you know so much about Rattigan?”

Dumfrey let out a heavy sigh. “He’s my brother.”