HAT ARE WE looking at?” Gazzy asked.

“I’m guessing… fish?” Iggy said, sounding bored.

“There’s a bunch of containers out on the ocean floor,” I explained to him. “Plus fish.”

“How deep are we?” Nudge asked, her nose pressed against the thick glass.

“Almost a thousand meters,” said Captain Perry. “More than three thousand feet. Not the deepest part of the ocean by any means but still deeper than most subs can go.”

“So they were counting on people not being likely to find it,” Fang said.

“Yes,” Brigid murmured, staring out the window.

“We’re moving in closer,” said Captain Perry.

“There’s writing on the containers,” I said.

“Shining lights on it now,” said Captain Perry.

This close, with the floodlights hitting them full on, we could see dim markings on the sides and tops of the barrels. Brigid’s radiation detector was practically in hysterics, and I wanted to say, “Okay! We get it! There’s radiation! Now shut up!”

“There are Chinese characters,” said John.

I looked at the barrels and saw they were also stenciled with English words. “It says, Danger, Keep Away.” I read slowly, peering through the water. “Property of the Chu Corporation. Huh. No surprise there. And they’re marked with some kind of yellow and black sign.”

“That’s the symbol for radioactive material,” said Brigid.

“Some of the containers’ lids are popped,” said Gazzy. “Like they’ve rusted open. I assume that’s an ‘uh-oh’ kind of thing.”

“I guess you were right about the radiation causing the monsters,” said Nudge.

“It hasn’t been proved yet,” said Brigid. “A scientist needs conclusive proof. But it does certainly look possible.”

“It’s all making sense now,” said John. “The Chu Corporation is dumping illegal radioactive material into the ocean. He created his army of robots to keep it hidden and protected. The CSM was doing a lot of work to bring ocean pollution to everyone’s notice, so we became a threat.” He rubbed his hands over his eyes, looking tired.

“Now what?” said Iggy. “Who you gonna call?”

A quiet voice in the hallway outside said, “Ghostbusters!”

Captain Perry and John groaned. “That phrase is ruined forever,” said John.

“Well, let’s get back up to the surface,” I said briskly, trying not to sound too eager. Knowing I could breathe under water was comforting, but at this depth, if I went out of the sub, I’d be mushed flatter than a pancake in less than a second. “We can call the EPA or the CSM or the navy or whoever, and tell them where this stuff is.”

Not so easy, Max, said the Voice.It’s never that easy. You should know that .

Okay, who saw that coming? Be honest. Everyone but me?

“Uh-oh,” said Angel.

“Double uh-oh,” said Gazzy.

I rushed back to the window and looked out, cupping my hands around my eyes. The sea was moving. Wait—no, not the sea…

It was a wave of Mr. Chu’s weatherproof all-terrain assassins. There were hundreds of them, and they were rushing toward the sub.

It was battle time. Again.