Coop pulled a paper airplane from his backpack and tossed it toward the safe. Metal scraped above them, and a steel pendulum with a razor-sharp blade that flared out at the bottom swung down from the ceiling, cutting across the width of the room.

Coop threw three more gliders, triggering three more pendulums. He could feel the breeze of their movement on his cheeks.

“Consider this my resignation,” said Phil. “It’s been swell working with you, but there’s this kitten puzzle I’ve been meaning to finish back home. I have all the corners done.”

“Shut up. You got me into this. Let me think. And don’t even dream about singing. I need to count these pendulums.”

“Why?”

“Because this wall sconce is loose and we’re going to fall in the next couple of minutes, unless I can . . .”

Coop leapt into the air as the first pendulum swung past. He just managed to grab the bottom and hold on as it moved in slow arcs, slicing through the air. Phil didn’t say a word. He just screamed.

Coop grabbed onto the shaft of the pendulum and pulled himself to the ceiling. There was a sort of axle there, running from the door straight across the room. From the top of the pendulum, he swung out onto the axle and climbed hand over hand across it, timing each handhold with the swinging of the pendulums.

It took several sweaty, painful, nerve-racking minutes to get there, but at the far end of the axle, he was finally able to swing down and drop onto the top of the safe.

Phil stopped screaming. “How did you know it would hold your weight?”

“I didn’t. But Babylon doesn’t want his safe falling to Shanghai, so whatever hocus-pocus he’s using on it must be strong.”

“That’s very reassuring,” said Phil. “Don’t mind me if I go back to screaming.”

“You can scream all the way home in the Missile. Right now, keep an eye out for more traps.”

“How are you going to open it?”

“I was cracking safes before I could microwave pizza. Besides, the DOPS smart guys gave me something to help.”

“Be careful.”

“What? Do you see something?”

“No, but I wouldn’t make getting in there as easy as guessing a combination.”

“Right.” Coop took out his collapsible grip and tapped it gently on the safe’s keypad. Something hissed.

“Gas!” screamed Phil.

“Thanks. I have ears,” said Coop as he took out a respirator and goggles from his backpack.

“You want me to scream it again? ’Cause I can do it louder.”

Coop touched the grip around the rest of the safe door, but nothing happened.

“We should have brought Morty with us,” said Phil. “He could get this thing open lickety-split.”

“Do you really think all three of us could have made it this far?”