But I barely sleep that night, or the next, or the night after that. We make it to the motorway and start heading north, crawling along at a snail's pace, each step bringing us closer to Holme. On the third day we see a group of people a way behind us on the road, moving in our direction. We speed up until we lose sight of them, then hide ourselves at the side of the road and wait for them to pass us by, but they never do. Eventually we get back on the road and keep moving, with many a nervous glance back the way we came.
We find food and water at a small village that we pass through. We see more craters, most of them overgrown and dead, but two or three that are horrifyingly alive. The first time Lisa sees one of the outsized monsters that squat in the living craters she stands and stares for almost ten minutes, mouth open in horror.
"Come on," I say eventually. "Let's get moving. Best to put some distance between us and it, yeah?"
I count the miles as they pass. We're making less than ten a day, but even that is a struggle. For a few days the cold weather deepens and we wake each morning to frost on the ground. We wrap up warmer and forge on. Lisa is never comfortable anymore, the baby kicking all night to keep her awake. We talk little, all our energy spent on walking.
I try to guess how much longer the journey will take. Ten days, I think at first. But ten days come and go and we're barely halfway. Twenty then, or maybe a month. We wander past ghost towns, through frozen traffic jams, clamber over trees that have fallen across the road, skirt around great cracks and craters in the ground.
Still I struggle to sleep. The exhaustion is all way through me now, in my very bones. Lisa, and the thought of getting her to Holme is the only thing that keeps me going.
Which is why I'm surprised when one morning when we sit down to rest she says, "I'm sorry, David."
Lisa's looking at the ground, her face pink with cold and exhaustion. "I'm slowing you down," she says. "You would be there already if it weren't for me."
"Lisa..." It takes me by such surprise that I don't know what to say to her. I almost laugh, but I can see that she's really upset. "Lisa, there wouldn't be any point without you. You're the reason...if it weren't for you..."
"But what if something happens?" she says. "What if you get hurt or killed because of me?"
"If it weren't for you," I say, "I wouldn't even be alive right now."
She wipes quickly at her eyes. "What do you mean?"
I hesitate for a moment, but only for a moment. It seems so long ago now that it's really not that hard to tell her. It's as if I'm talking about something that happened to somebody else. "Back then, before I met you--when it was just me on my own--I'd wake up every morning and try to kill myself. I just...I'd lost everything. I just wanted it to end. And then...well, then I met you. You gave me a reason to keep living."
Lisa blinks at me, looking astonished. The she starts to cry. I hold her until the tears dry up. And then she stands, and we move on together down the road, hand in hand.