The water has loosened clay on some of the banks, so there are slips and little heaps of yellow dirt on the road. Luckily, nothing so serious that we have to stop and get the spade out of the back of the car. Will just drives around them. But on the other side of the Sound we come to a tree lying across the road. It’s a skinny little manuka, but it’s still attached to its upturned roots in a mound of mud nearly as big as the car. There is no way we can move it.

Will and I stand in the rain, staring at it. We have a blunt spade to shift dirt but no saw or axe to take care of a tree. We tug at the manuka, which is no thicker than my wrist, hoping that it will break, but it keeps whipping back to its original position. It’s about half a metre above the ground and it blocks the entire road.

“This is ridiculous,” says Will.

I agree. “We need your bush saw.”

“It’s not my saw, and anyway it’s busted. There’s a rope in the car. Maybe we can tie it to the top of the tree and pull it up high enough for the car to get through.”

I shake my head. “That’s too hard. Let’s try the other way, push it against the ground and drive over it.”

We lean on the skinny manuka tree and it sinks a little. Then we both sit on it. It feels like a spring beneath us. We could bounce on it all day and not break it.

“We don’t have to push it right to the ground,” Will says. “If it’s just above the road, the wheels will do the rest.”

Grandma has wound down her window. She puts her head out. “What’s happening?”

Will and I look at each other, thinking the same thing. “Will she do it?” Will asks.

I walk back to the car and brush my dripping hair away from my eyes. “There’s a little tree across the road. If we push it down, Will can drive over it.”

“Then push it down,” she says.

“I’ve tried sitting on it, but I’m too light.”

She doesn’t even grumble. She grabs the door handle and swings her feet out to the muddy road. Will and I help her over to the tree and find the right place for her to sit. I sit beside her. It works. The springy tree collapses under her weight and settles close to the road.

Will runs back to the car. There isn’t much space between Grandma and the edge of the bank, but he drives carefully, edging the car into the gap. As the front wheels touch the tree, it moves as he said it would, down against the ground, then bump, bump, the car is over it and on the other side.

I help Grandma to stand. We are both wet but she is not complaining. “Where there’s a will there’s a way,” she says to Will when he comes back with a couple of towels. He grins, and neither of us tells her that people quote that one at him all the time. Usually, it comes from teachers who want him to do better at sport, but from Grandma it’s a compliment.

We sit in the car to dry ourselves. We’re on a hill overlooking the arm of the Sound, water everywhere on land running down into the sea. Through the rain we can hear the rush of waterfalls, even though we can’t see them. Grandpa is quiet now. I think he’s in a lot of pain. His head is on a cushion against the window; his eyes are closed but he’s not asleep.

We have only half an hour before we reach the main road that will take us to Blenheim. Will is worried about taking the car into traffic. I’m sure he can do it all right, but people will see a little kid at the wheel. I wish I knew how to drive. At least I look about the right age.

My hair is no longer dripping. I feel in my bag for my hairbrush, and my hand stops on my phone. Something makes me pull it out and switch it on. “Hey! I’ve got a signal!”

Will is drying his head. “You’re not ringing your friends!”

I hold up the phone. “It’s a strong signal. Three bars. Grandma, you hear that? My mobile phone is working!”

“That’s a no-brainer!” says Will. “Put the stupid thing away!”

“Shut it, poo-face! We can call the hospital!”

Grandma leans over my seat. “Can you ring that thingy from here?”

“What’s the hospital number?” I ask her.

“You don’t need that,” she says. “Just call 111.”