We first got word of the trouble when a too-high proportion of people started killing themselves. Lobjobs, mostly, and usually off the top of prominent buildings. It was a public display, a grand exit. It was fairly obvious that an advert was to blame, but tracking it down to source was proving difficult. The adverts they've got these days, it's not just buying the latest gizmo; they can make you do anything. That's why we have the strict controls; that's why we're here, the commcops. Someone should've realized that bad people would get hold of the technology, because don't they always? So, we'd had killer transmissions before, but never this successful, and never this prominent. It was the number one job on the crime sheets, and we were getting nowhere on it, until a victim came forward.

This guy was in a right state, babbling mainly, and screaming about a stairway, 'a golden stairway, endlessly… endlessly…' Eventually, we got some sense out of him. He'd been sitting at home, quite peacefully, watching a game show on television. His wife was with him. The children, thankfully, were upstairs at the time. They missed the advert. The advert that came out of nowhere, just sitting in between all the other adverts that plagued the TV that night, and nothing strange about it, just this image of an endlessly rising stairway. No words with it, no slogan, but that was the norm. The usual freeze. The freeze and the thrall. Legal ads were low-level interference, and you could easily resist their temptations with a little will-power. So they'd thought nothing of it, this man and woman, except they both dreamed that night of the stairway, and of going up it, and what they might find there.

The next day, two in the afternoon, the wife had thrown herself out of the top-storey window of the office where she worked. That was five days ago, and distraught as he was, and full of suffering for his lost wife, how could the husband not want to join her? This is when he read about the spate of similar suicides. God knows what resources he had conjured up to get himself as far as the commcop station.

Brendel wanted to place him under arrest, for his own safety, but the authorities would have none of that. So we filled him up with the maximum dose of spoiler juice, and then let him go. He lasted two days. Of course, we had a cop on his tail the whole time. Did no good; he shook the cop off, just for a minute.

A minute's a long time when you're falling…

Things got bad then, because the story broke loose. The media were hounding us, and Brendel was on a sharp edge. She cancelled all leave, tripled the bonus for the Apex score, got the lab boys working full-time on the transmission source. The only good thing they could find was how the stairway ad would only ever appear on one receiver at a time. What we call a narrowcast. It would turn up on a private TV, a computer screen, an arcade game. Never on a public system, like a cinema screen. As though the advert was picking people off, one by one. Sniper mentality. We tried putting out our own adverts, warning people not to watch, or play, or in any way to have serious leisure time. We did the usual pointless appeal to the TV and game companies, asking them to suspend all transmissions. Like, yeah, sure we'll cut off our money supply, just on some unsubstantiated claim about a killer ad. Get out of here. So we distributed free scatterglasses, cheap and nasty ones, which is a bit like getting flotsams to wear pinstripe suits. No deal, and you can't reach everybody, not all the time, so I guess we all got to feel like warriors, us commcops, naked on the streets against this invisible, deadly enemy. How else explain what Parker did, what I let him do?

It was a Sunday night, quiet time in the all-night arcades. The usual flots and jets to unfreeze, no big deal. Parker was getting bored, and itchy. He was expecting more of the job, of course he was, young like that; I was the same. Pretty soon you get to find out that being a commcop isn't quite like the recruiting images, and I tried to give him the real package. Stupid kid wouldn't listen, going crazy he was, with fighting talk about how he was gonna take this stairway fucker out, once and for all. He was hot for it, and I couldn't help but get a secret pleasure, remembering mainly, remembering how it had been when I first started out.

We found a group of flots gazing full on at a game screen. Locked solid they were, and as we came up, I was dreading seeing the stairway there. This had been my fear, the last few weeks: coming across a spectator in thrall to the killer. Luckily, it was just a slowly rotating pair of plastic trainers up there on the display, saying in secret, 'Buy me! Buy me! Buy me now, you stupid suckers!' Easy game, because this had all the design flair of a camel's arse, and was obviously a trans from Minskey's Muscle, a sports shop only two blocks away. Parker was mad keen to shoot the trainers himself, he had the gun out and loaded and everything, so I said, 'This one's yours, kid', and went off to slap the fine on Minskey.

Big mistake. Because it took longer than I thought, what with Minskey putting on a show, and his pumped-up sales assistants hanging round in sub-pensive mode. All around me were banks of screens playing out the same commercial, and variants thereof, and here this guy was, claiming he 'didn't never have such bad adverts, no ma'am, not never. See now, these good adverts, clean adverts, no nasties. No freeze. See?'

All the time I was hoping Parker would hurry up. I needed the back-up. What was the kid doing? Surely he'd done the deed by now, come on. In the end I had to walk out of there empty-handed, which pissed me off. So I was all set to give the grief to my so-called partner. I was acting mad for my own failure, I know, and maybe the kid was having trouble, it's just that I can't stand not making a clean case of a job. And by the time I get back to the arcade, the place is deserted, all the games standing empty, forlorn with abandoned play. No flots, no jets, no Parker. So I'm looking round and getting worried, when I hear this noise from the next aisle, a kind of screaming sound. Like human, through the mincer. Straight off, I should've called for back-up. Instead I was just running over there, towards the bad sound, because the sound got me in the guts. Bad reaction getting to me. Round the corner, I see a bunch of people going crazy outside this one shop. The screaming coming from them. OK, get up close, and slow down, slow down, check the situ, play the book. The shop was a dark-eye, shut for business. Abandoned, read the slashed-on sign across the window. The door thinly open. OK, what's the score here?

'My sister! My sister! Help her! My sister!'

One freaked-up flotboy, coming right on at me, making me sweat, so desperate. And someone else, saying, 'It's the stairway thing, pretty sure it must be.'

'She's in there?' I ask.

'Get her out!' screams the boy. Keeps on screaming.

'Where's my colleague?'

'Uh?' Voices.

The other cop, where is he?'

'He went in.' Voices all round.

Shit.

I look around the crowd, most of them quiet now and just looking at me, as though I could save one of their kind, but all I was thinking about was Parker, that stupid fucker, going in alone. I think that's when I got round to calling HQ for the back-up van, Apex coding. Of course, I didn't wait, how could I? Instead, pull the mask down tight, load the spoiler, kick the door wide, step through.

Dark. Dark in there. Only the faint buzz of colour through the scatter, vapour from some screen, way back. No sign of Parker or the girl, and what the fuck was a television doing on, in this dump? Moving through, beam on, I see signs of cheap habitation, spread duvets, camping stoves, pots and pans. Flot squat. In the dark my beam flashes on something, a rolled-up duvet or something, then I see it's a kid, a young girl. She's lying on the ground, all cradled up in herself, gently rolling, back and forth, back and forth. And when I bend down, turn her over, and she opens her arms for me, I see this amazing thing - she's got a mask on. A commcop mask.