We are twenty yards from the wall, and Jesmond the nurse is about the same distance behind us when we see movement inside the van. A large figure in luminous green running gear emerges from the side door, loping toward the wall and shouting, “Lift her over!”

Sass Hennessey?

A second later, she’s standing on the wall as we stumble to a halt. We can’t look back, but I can hear Jesmond’s footsteps getting closer. He’s only a few paces from us when Sass reaches down and, with an almighty lunge, grabs the wheels of the chair. As she pulls up, Ramzy and I push, and the whole thing—the wheelchair with a squealing Dr. Pretorius in it—is over the wall, and Sass is pushing it to the open-sided van.

Ramzy’s over the wall and I’ve just about made it when I feel a strong hand on my arm and a vicious pull back.

“Not so fast,” says Jesmond, spinning me round to face him. His white-blond hair is stuck to his forehead and he’s panting hard. “What…what the hell are…are you doing?” he gasps, not lessening his grip, even though I’m wriggling.

I don’t get a chance to answer, as I see him looking over my shoulder with genuine fear in his eyes. I hear a terrible scream and turn my head to see Sass, crimson in the face, running from the van toward us, emitting a war cry and circling Dr. Pretorius’s walking stick around her head like a helicopter blade.

“Aaaaaaaaarrrgghhh!”

Nurse Jesmond doesn’t say anything. He just emits a little squeak and lets go of my arm as the full force of Sass’s bulk hurtles toward him.

I take my chance and run as Sass lowers the walking stick and utters a gentle, “Sorry.” Then she turns to catch up to us, leaving Jesmond gawping in astonishment.

The campervan is already moving off and I’m the last to jump in, just behind Sass, and pull the door closed behind me.

I have now, officially, no idea what’s going on. I stare at Sass Hennessey, who is sitting hunched on the flat floor of the van, hanging on to Dr. Pretorius’s wheelchair to stop it rolling around inside. Dr. Pretorius is muttering, “Are there no brakes on this cockamamie thing?”

I eventually say, simply, “Saskia?”

“I was just…just on an evening run,” she pants, still red in the face from her demented charge at the nurse, “when your brother’s car stalled at the lights at the end of the road.”

Clem looks at us in the rearview mirror and shouts back over the roar of the engine. “I needed a jump-start, so I asked Sass!”

“Yeah. And I figured he could give me a lift home in return. Good job I was hanging on: I think he tried to drive off without me!”

I think that that is exactly what Clem did, but I keep the thought to myself. Instead, I say to Sass, “But…but why? Why do all that?”

She looks at me levelly, or as levelly as is possible in the rocking campervan. She says something that sounds like, “Friends help friends, eh?” but I can’t be hearing properly over the rattling.

This much is pretty clear, though: a campervan containing Clem, Sass Hennessey, me, Ramzy, and Dr. Pretorius (in a wheelchair) is belching exhaust fumes and puffing back along the road toward Whitley Bay seafront, on our way to saving the world.

It is not going to be easy, though.

I scramble over the others to claim a place on the front bench seat next to Clem. We have just driven past the car labeled ARMED POLICE that we saw before, and that’s when I see a gray, brown, and white shape dodging a car and lolloping slowly over the grassy hill that leads down to the beach. I scream and Clem flinches.

For a moment—just long enough for me to be absolutely certain it’s him—Mr. Mash pauses at the top of a dune before disappearing from view. At the same time, the police-car door opens, and an officer in body armor gets out, watches to see where Mr. Mash is going, then goes quickly to the rear of the vehicle and opens the trunk.

He’s going to try shooting my dog.

“Look!” I shout. “It’s Mr. Mash. He’s in trouble. Turn left, turn left, Clem, now!”

“I can’t,” he says. “There’s no road!”

He’s right, of course—there is no road to turn left onto. I know, though, that Mr. Mash’s life is at stake, and I’m not going to ignore it. Leaning over, I grab the steering wheel and pull it sharply, causing the van to lurch violently to the left. There’s a screech of brakes behind us, a honking of horns, a crunch of steel, and a tinkling of glass as cars collide.

Beneath us is a clanking metal sound: the impact of mounting the pavement has caused something to come loose from the campervan, and then we’re off the road, up the pavement, and driving on the grass.

“There goes the exhaust!” shouts Clem. The engine is even noisier than before.

I’ve opened the side door of the van and am out while it’s still moving, running over the low hill and shouting, “Mashie! Mashie!”

At the same time, by the police car, the officer has taken a rifle out of the trunk and is screwing the barrel into the stock.