He handed me another evidence bag. "See anything wrong?"

It was a wallet, white fake leather, sewn with a butterfly in silver thread and swiped with faint traces of blood. "It's too clean," I said. "You said this was in her front jeans pocket, and she bled out all over her lap. This should be covered with blood."

"Bingo. The pocket's stiff with it, soaked through, but somehow this barely gets stained? The torch and keys are the same: not a drop of blood, just a few smudges. Looks like our boy went through her pockets and then wiped her stuff clean before he put it back. We'll have the Bureau fingerprint everything that'll stay still long enough, but I wouldn't bet on getting anything useful. Someone was being very, very careful."

"Any sign of sexual assault?" I asked. Sam flinched. I was way past that.

"Cooper won't say for sure till the post-mortem, but nothing on the preliminary points that way. We might get lucky and find some foreign blood on her"--a lot of stabbers cut themselves--"but, basically, I'm not holding my breath for DNA."

My first impression--the invisible killer, leaving no trace--hadn't been far off. After a few months in Murder, you can tell One of Those Cases a mile away. With the last clear corner of my mind I reminded myself that, no matter what it looked like, this one was not my problem. "Great," I said. "What do you have? Anything on her, other than she's in Trinity and she's running around wearing a fake name?"

"Sergeant Byrne says she's local," Sam said. "Lives at Whitethorn House, maybe half a mile away, with a bunch of other students. That's all he knows about her. I haven't talked to the housemates yet, because . . ." He gestured at Frank.

"Because I begged him to hold off," Frank said smoothly. "I have this little idea I wanted to run by you two, before the investigation gets into full gear." He arched an eyebrow towards the door and the uniforms. "Maybe we should go for a wander."

"Why not," I said. The girl's body was doing something funny to the air in there, fizzing it, like the needle-thin whine the TV makes on mute; it was hard to think straight. "If we stay in the same room for too long, the universe might turn into antimatter." I gave Frank his evidence bag back and wiped my hand on the side of my trousers.

In the moment before I passed through the doorway I turned my head and looked at her, over my shoulder. Frank had switched off his torch, but pulling back the brambles let in a flood of spring sun and for the split second before my shadow blocked it again she rose up blazing out of the darkness, tilted chin and a clenched fist and the wild arch of her throat, bright and bloodied and relentless as my own wrecked ghost.

That was the last time I saw her. It didn't occur to me at the time--I had other stuff on my mind--and it seems impossible now, but those ten minutes, sharp as a crease pressed straight across my life: that was the only time we were ever together.