“The specimen Nemo brought back is a mature one,” the doctor said. “The end-stage form. The one that was injected into you was microscopic. You didn’t even know it was there. But once it gets as large as the one you retrieved from the bunker, it’s likely too late to reverse the effects.”

“How long does it take to get that big?” said Nemo.

“We don’t know,” the doctor admitted. “My guess is quite some time. Six and Sam have been infected for less than a week at this point, so I’m hopeful that the damage isn’t irreversible. If we get the antidote into them soon.”

“How soon?” asked Max.

“As soon as possible,” said the doctor, without elaborating. But the expression on her face worried Max.

“Where did this thing come from, anyway?” Nemo asked. “Like, is it just out there in the world? Could it infect anyone with a Legacy?”

“I don’t think so, no,” said Dr. Fenris. “My guess is that it was created by the Mogs you had a run-in with. It’s unlike any parasite I’ve ever seen before. Here. Take a look.”

She beckoned them over to the microscope. Max leaned down, peering through the eyepiece. He saw something that looked like three big purple blobs. “What are those?”

“Those are the toxins created by the parasite,” Dr. Fenris said. “Now watch what happens next.”

She placed the tip of a thin pipette on the surface of the glass slide in the microscope. Max saw a thin stream of tiny red bubbles come out.

“What’s that?” Max asked.

“Those are the antibodies from your blood,” the doctor explained.

As if they sensed the antibodies, the toxins moved towards them, like monsters hunting their prey. Max felt his heartbeat quicken. For some reason, watching the toxins attack his blood terrified him. But then something interesting happened. The antibodies attacked, throwing themselves against the walls of the toxins until they broke through. Then they rushed in, filling up the purple blobs with red and consuming them.

“That’s awesome,” Max said, stepping aside so that Nemo could have a turn watching.

“That’s science,” Dr. Fenris said.

“So if Max’s body can do this, why can’t Six’s and Sam’s?” Nemo asked.

“Every body is different,” Dr. Fenris said. “In medicine, we like to say that immune systems are built, not born. That means that your body develops defenses based on what it’s exposed to over the course of your life. For some reason, Max’s body has developed a way to fight the parasite. It could be because he was exposed to something similar in the past. Or his specific Legacy might have something to do with it, since his ability changes his brain function. Or his body could just be better at fighting invaders.”

“In other words, you don’t really know,” said Nemo.

Dr. Fenris smiled. “The important thing is that it seems to work.”

Listening to her talk, Max had a thought. “But it might not work in Sam and Six, then, right? I mean, if their bodies are different from mine.”