“I DON’T THINK WE NEED TO INVOLVE RILEY AND Raeburn,” Calvin said.

They were in Calvin’s tree house, which had become their unofficial hangout. About twenty feet off the ground, it was accessible by climbing up the tree and entering through a hinged opening in the floor. About the only thing Emmet didn’t like about it was leaving Apollo on the ground. They hadn’t yet figured out a way to safely get Apollo up there with them.

“Why not?” Emmet asked. “They’re smart. And Raeburn knows a lot about bats. And by now I bet she’s learned everything there is to know about hornets.”

Emmet sat gingerly on one of the beanbags. He’d spent three days in the hospital, until doctors were sure he was going to be okay. Except he was going to need more rabies shots for about a zillion days or so, it seemed.

“You still look pretty beat-up,” Calvin said.

“I am pretty beat-up,” Emmet said. “I got attacked by bat-a-hornets!”

“Blood Jackets,” Calvin replied.

“Don’t change the subject. You want Dr. Catalyst stopped, don’t you?”

Calvin hesitated a moment. “Yes.”

“But?”

“I’ve known you for what? A few months now? You’re not like other people. This guy is really dangerous. I get that you wanted to save your dad and Apollo and all, but you’ll go charging after him. I have enough to do just trying to keep you from getting injured … or worse. I can’t keep my eye on everyone.”

Emmet knew this was partly true and partly false. Calvin was cool in a crisis — charging at a Pterogator or breaking into an abandoned amusement park. But the real reason he was protesting is that being around Riley made him nervous.

“Being around Riley makes you nervous,” said Emmet.

“No, it doesn’t!” Calvin protested.

“Yes, it does. And you’re not responsible for everyone’s safety. But, regardless, we need all hands on deck. We don’t need Riley and Raeburn to go anywhere dangerous, but we could use all the brains we can get. Besides, I think Riley and Raeburn can take care of themselves.” Emmet shuddered, remembering a few weeks ago when they were attacked by the Muraecudas in the ocean, and how Raeburn used her snorkel like a weapon to get the giant beast to release its grip on Stuke. She was pretty fearless.

Calvin sighed. By now he must have learned it was useless to argue with Emmet.

“Do you ever wonder … ?” Calvin said.

“Yes. I wonder all the time. Can you be more specific?” Emmet asked.

“How Dr. Catalyst is always a step ahead of us? When he took your dad from the swamp, he had to know where your dad was going. I mean, what are the chances he’d just show up where your dad was? And at the beach with Stuke, he sets those things loose right where we were. And even when he took Apollo … I suppose he could have been waiting in the canal, but how did he know for sure you were even going to be home? It’s like he always knows where we’re going to be.”

Emmet considered this a moment.

“Do you think he’s having us followed?”

“Maybe,” Calvin said. “But that would take a lot of planning and manpower. He’d need more than just himself.”

“He has Dr. Newton. If Dr. Newton isn’t really Dr. Catalyst, maybe he’s an accomplice. And that’s how he keeps track of us at school.”

“I don’t think so,” Calvin said. “If the Newt is Dr. Catalyst, then he just took himself out of the equation. If he was keeping an eye on us, why would he pretend to be kidnapped?”

“He knew we were closing in. And so he faked another crime, like he faked his death in the Everglades. Which, I would like to point out, no one believed me about, and I turned out to be right. Again.”

“Yeah, we know. But I still don’t think he’s following us,” Calvin said. He stood up and started pacing.

“Why?”

“Because when we showed up in the swamp to rescue your dad, and at Undersea Land to save Apollo, he was surprised. We set off alarms, and he came running. But he didn’t know we were coming. If he did, he would have just taken off or moved them to another location. We surprised him then, but he knew where we were those other times. Either he has someone on the inside, or …” Calvin let the words trail off.

“Bugs!” They both said at the same time.

“He’s got listening or tracking devices planted, probably on our parents’ cars, and at the NPS headquarters. Maybe even in our houses!” Emmet said.

Calvin nodded grimly.

“Could he have done that? Bugged the park headquarters?” Emmet asked.

“It’s a federal facility, and it has security and all that, but it’s not like the CIA or the Pentagon. If you were determined enough, you could probably wire it for sound, at least. There isn’t anything top secret going on there, so they don’t have any reason to suspect that stuff. From what we’ve seen, he has the resources,” Calvin said.

“So,” Emmet said, smiling, momentarily forgetting about his painfully swollen face and his impending rabies shots. “This is how we’re going to catch him!”

When their parents arrived at Calvin’s house, they told them their theory.