It's been a long day, a long week, and I'm bone-tired as I get into the car to drive home. A small voice tells me it wasn't the best idea to go out tonight, to drive 60 miles for dinner after 12 hours in the office. But the small voice's invincible sidekick tells me a night out was just what I needed. And it has been lovely; relaxed friendly chat, catching up on news of friends, swapping stories of visiting guests, telling tales of office colleagues.
The road is dark and I'm the only one on it. No street-lights out here in the country, no headlights from passing cars.
I feel the waves of sleepiness rise up, feel the heaviness at the back of my eyes, I try to swallow down the weight and the lethargy. I know how quickly I fall asleep at home, how hard I fight to stay awake in front of the tv and how soon I lose consciousness the minute my head hits the pillow. I know how easily I could drop off now.
Bright cats-eyes dance on the road in front of me, then suddenly I feel them under the tyres and realise I've swerved, I pull back sharply to where I ought to be, to my side of the road. For a moment I'm wide-awake, blinking in panicked shock, but then the sense of slipping comes again.
Twenty miles to go, half an hour to home.
I turn up the radio, blast out the air-conditioning, gulp down great mouthfuls of cold air. I'm not really listening to the radio, the voices merge with the thoughts in my head; the conversations of tonight, the confrontations of the day, all mixed together in no clear stream, with no clear sense. I move my head from side to side, feel the muscles in my shoulders stretching, my spine clicks. I imagine someone pulling a string tied to the top of my head, lifting me up tall and straight.
As I pass a lay-by I think of pulling over, but I'm too stubborn to stop, too scared to sit at the side of the road by myself, so I drive on. I think of speeding up, perhaps if I get there quicker, I'll beat the almost irresistible weariness.
A huge lorry looms up out of the darkness, seemingly out of nowhere. The row of lights across the top of the cab dazzle me, shining out like stage lights on opening night. I blink awake and shrink back like a hidden creature retreating when a stone is overturned.
When I finally get home, the street is dark, our house is asleep; no lights at the windows, no lamp above the door. I'm strangely angry that there's no brightness to greet me; I want a lighthouse beam to recognise how close to the rocks I've been, to guide me safely the last few yards.
I fumble for the key, feel for the lock and guide it in. I feel clumsy and stupid; I know I'm not angry with the dark house but with myself; I know just how easily I might have been slipping, not into the dark comfort of home, but into another kind of darkness altogether.