The bags beneath Chatterjee’s eyes made clear what a toll these past weeks had taken on him. Bad news piling on top of bad news, and him the only adult in sight.

“So that means…” My brain was still a half step behind. “Patrick and I might have had different biological mothers?”

“Yes,” Chatterjee said. “If the genetic code that makes Patrick immune is from the maternal side—”

Patrick looked crestfallen. “Then Chance wouldn’t be immune like I am.”

For a moment silence reigned.

I thought about how much bigger than me Patrick always was. Stronger, too. The way everyone joked about how little family resemblance we had. And our personalities also had been different from the gates. Our interests and talents seemed to pull us in different directions from the beginning.

“Wouldn’t you know if the egg donor was the same?” Patrick asked. “I mean, you were our doctor. You delivered us. Wouldn’t that be in a file somewhere?”

“I’m afraid that information was kept confidential even from me. It resides somewhere in a computer system at the donor bank.”

My head felt heavy, filled with smog. I thought about what Alex had told me in the cabin about her father and my mom: They were gonna get married, have kids, the whole thing. Then Dad broke up with her after graduation. I don’t know what it was. Cold feet, fear, whatever. But he never forgave himself for it. Or her.

He’d broken it off with my mom because he’d found out she couldn’t have kids. Or at least she’d thought she couldn’t.

When I came back from my train of thought, Dr. Chatterjee was staring at me, looking dismayed.

“Okay,” I said, trying to keep the disappointment from my voice. “Thanks for telling us.”

“I’m sorry to drop this bombshell on you in the middle of everything else,” he said.

“That’s what the world is now,” I said. “One bombshell after another. We might as well get used to it.”

Patrick turned to me. “If I could trade places with you and give you my immunity, I would.”

“I know,” I said. “But I wouldn’t take it.”

He put an arm around my neck and tweaked me into him, hard. It hurt and felt good at the same time.

Dr. Chatterjee rose, and we started to head out.

“What are you gonna do about Ben?” I asked.

Chatterjee halted, his leg braces clanking. “We don’t know that he loosened those valves, Chance.”

“Yes,” I said. “We do.”

“You’re making accusations without evidence. We can’t act on that. We can’t live like that. Think what this community would deteriorate into without rules in place.”

“Ben said it himself,” Patrick said. “There have to be new rules. The old ones won’t work anymore.”