The long day is done, and as the world turns to night I know I will dream. I know what I'll be dreaming about. I even know the time, the place.

Yet even as I feel the blaze of the sun and listen to the low, hypnotic buzz of seasonal insects (a small, brain-shaped cloud of midges hang above nearby bushes) I realise the detail - the collected colour of the flower bed, the perfume of those tamed blooms - is too pedantically correct to be "real". It is life, but not as I know it.

But know it I do. When I glance down I will see a grass stain on the left leg of my cricket whites. There. I stare at the jade smudge, remember my original irritation, only memory and movie grammar get mixed up, because the stain, a trifling disfigurement, is, in extreme close-up, as big and as emerald as Ireland. It's oddly wrong, and yet oddly right.

That's because Derek is dead. And that's because he is not. I expect him any moment now, though he left some hours before, and what does it matter, because this is his birthday party in the park. I remember. He was - is - 22. I stretch my hand out and touch the wicker hamper. Simon has the tartan blanket, Stephen his ghetto-blaster, Lou the cake. Everyone sweats.

Lou looks at the football players on the other side of the railings and repeats himself: "In my next life I want to be a bucket and sponge." Simon says: "I'm going to be a pair of shorts." And we giggle, only my skin and muscles pull like melting toffee: loose, strange, wrong. Spoils deposited, the boys wander to the railings, leap and struggle over. Lou says: "Catch you at half time!" I reply: "Derek's dead." Simon says "That's old news."

Derek's hands on my shoulders are warm - oh God, I think, his hands are alive - and the fingers dig in gently, massaging, soothing. Then his arms circle my chest and his breath is in my ear and I can't help it, I can't, I'm sobbing like an infant, chest racked, nostrils running, in what my mother would call "floods". Derek makes these comforting, calming noises as I cut deals with the Deity, asking Him to not to do this, that I've done with long goodbyes, to let me wake up.

I nearly do. For a second the pillow is beneath me, soft and damp, as I am strung between two states. Derek soothes, "No, John, not yet" and, yes, he's 22, brown hair and blond streaks, smile serene, in command. I've forgotten how pretty he was (is). "I'm crying in my sleep," I inform him, idiotically. He nods, brushes the hair from my face, which makes me start, until I recall I did have long hair then (now).

"How was it?" he asks. I tell him. Some of his family finally there in that small, stifling box where the air conditioning was fitful when not downright thoughtless, how the men wore second-best suits and the women cheerful summer dresses, how I had taken his Filofaxes, engaged auto-pilot and rung the requested names, the former lovers, passing fancies, old pals and severed ties. "The Ex-Files," I joke. Derek grins. Tears on the telephone as the afternoon wore away: gasps, cries, expressive silence, the rages against fate, luck, karma. I mention the man in America he lived 12 years with: "He said he always thought that one day you'd appear on his doorstep asking if you could have a second chance. He said he knew it was childish, but he couldn't help wishing." Derek shrugs, sighs, "No, you can't help wishing."

"You left the room," he says. It's not a question. I couldn't stay, didn't want to hold his skeleton hand or stroke his clammy yellow skin. By then it was only his body, not his spirit. That had flown. Did I do wrong? "John, it's fine," Derek says, "you've been great." That does it. "Enough tears," Derek cautions, but I'm embraced anyway. It hurts so bad. "Now listen," Derek says. "This was a day when we were perfectly happy. We imagined perfect happiness would be found in a night club with mirrored walls or in a stranger's kiss. But we were happy right here. We simply didn't recognise it. It comes and goes ... What are you doing tomorrow?" "Clubbing," I answer, perversely, hoping for a laugh. Right on target. Derek squeezes me hard: "Some dance to remember, some dance to forget. The Eagles. Way before their time."

And we sit and talk, until memory lane is jammed. I imprint each moment: his eyes, his shirt, his aftershave. I don't want to forget.

"I have to be going," Derek says. I want to answer, No, but his lips brush mine, he shakes my hand, which he never did before, and he heads for the gates, lifting his voice to say that one day we'll have lunch and wear big picture hats and endangered species, like proper girlfriends. I say nothing, but watch, because even if I dream of Derek again, this is the last time I will ever truly see him.

"Hey, John!" Derek turns, spins on the spot, shouts as loud as restored lungs will allow: "The best days of our lives!" I holler: "I hear you!" I do hear him. And I feel it, feel this fleeting, perfect happiness. I call out: "Derek ..." But he's leaving. And as he does, my friend begins to blur, to boldly go, a pavement painting caught by the rain, here and gone, leaving nothing save a hint of the artist's purpose for the rest of us to reach for, and puzzle over.