I gave her the number of the fax machine in my office, and I did not let her know my irritation. But I did give her a hint.

'Mary, in the future, it's best if you let me know about my cases before you start sending lab results to others,' I said calmly.

'I'm sorry,' and I could tell she very much was. 'The investigator called at five as I was halfway out the door.'

The reports were in my hands two minutes later, and McGovern opened her battered briefcase to retrieve her copies. She watched me as I read. The first was an analysis of the metal-like shaving that I had recovered from the dead woman's cut to the left temporal region. According to the scanning electron microscope and energy dispersive X-ray, or SEM/EDX, the elemental composition of the material in question was magnesium.

As for the melted debris recovered from the victim's hair, those results were just as inexplicable. A FTIR, or Fourier transform infrared spectrophotometer, had caused the fibers to selectively absorb infrared light. The characteristic pattern turned out to be that of the chemical polymer polysiloxane, or silicone.

'A little strange, don't you think?' McGovern asked me.

'Let's start with magnesium,' I said. 'What comes to mind is sea water. There's plenty of magnesium in that. Or mining. Or the person was an industrial chemist or worked in a research lab? What about explosives?'

'If potassium chloride came up, then yes. That could be flash powder,' she answered. 'Or RDX, lead styphnate, lead azide or mercury fulminate if we're talking about blasting caps, for example. Or nitric acid, sulfuric acid, glycerin, ammonium nitrate, sodium nitrate. Nitroglycerin, dynamite, and so on and so on. And I will add that Pepper would have picked up on high explosives like that.'

'And magnesium?' I asked.

'Pyrotechnics, or fireworks,' she said. 'To produce the brilliant white light. Or flares.' She shrugged. 'Although aluminum powder is preferred, because it keeps better, unless the magnesium particles are coated with something like linseed oil.'

'Flares,' I thought out loud. 'You light flares, strategically place them, and leave? That could buy you several minutes, at least.'

'With the appropriate fuel load, it could.'

'But that doesn't explain an unburned turning or shaving of it embedded in her wound, that would appear to have been transferred by the sharp instrument she was cut with.'

'They don't use magnesium to make knives,' McGovern observed.

'No, nothing like that. It's too soft. What about the aerospace industry, because it's so light?'

'Most definitely. But in those instances, there are alloys that would have come up during testing.'

'Right. Let's move on to silicone, which doesn't seem to make any sense. Unless she had silicone breast implants before they were banned, which she clearly didn't.'

'I can tell you that silicone rubber is used in electrical insulation, hydraulic fluids, and for water repellency. None of which makes sense, unless there was something in the bathroom, maybe in the tub. Something pink - I don't know what.'

'Do we know if Sparkes had a bathmat - anything rubbery and pink in that bathroom?' I asked.

'We've only begun going through his house with him,' she said. 'But he claims that the decor of the master bath was mostly black and white. The marble floor and walls were black. The sink, cabinets, and tub, white. The shower door was European and wasn't tempered glass, meaning it didn't disintegrate into a billion little glass balls when the temperature exceeded four hundred degrees Fahrenheit.'

'Explaining why it basically melted over the body,' I said.

'Yeah, almost shrink-wrapped it.'

'Not quite,' I said.

'The door had brass hinges and no frame. What we recovered was consistent with that. So your friendly media tycoon's memory holds true at least on that score.'

'And on others?'

'God only knows, Kay.'

She unbuttoned her suit jacket as if it suddenly occurred to her to relax, while she paradoxically glanced up at the clock.

'We're dealing with a very smart man,' she said. 'That much all of us know.'

'And the helicopter? What do you make of that, Teun? I'm assuming you've gotten word about the little white Schweizer, or Robinson, or whatever it was that the farrier saw two days before the fire? Perhaps the same one you and I saw two days later?'

'This is just a theory,' she said. 'A groping one at that, okay?'

Her look was penetrating.

'Maybe he sets the fire and needs to get to the airport fast,' she went on. 'So the day before, the helicopter does a recon over the farm because the pilot knows he'll have to land and take off after dark. Following so far?'

I nodded.

'Saturday rolls around. Sparkes murders the girl and torches his place. He runs out to the pasture and gets on the helicopter, which transports him somewhere near Dulles, where his Cherokee is stashed. He gets to the airport and does his thing with receipts and maybe baggage. Then he makes himself scarce until it's time to show up at Hootowl Farm.'

'And the reason the helicopter showed up on Monday, when we were working the scene?' I then asked. 'How does that fit?'

'Pyros like to watch the fun,' she stated. 'Hell, for all we know, Sparkes was up there himself watching us work our asses off. Paranoid, if nothing else. Figured we'd think it was a news bird, which we did.'

'This is all speculation at this point,' I said, and I had heard enough.

I began rearranging the infinite flow of paperwork that began where it stopped and stopped where it began. McGovern was studying me again. She got up and shut the doors.

'Okay, I think it's time we had a little talk,' she said. 'I don't think you like me. And maybe if you come clean about it, maybe we can do something about it, one way or another.'

'I'm not sure what I think of you, if you must know.'

I stared at her.

'The most important thing is that all of us do our jobs, lest we lose perspective. Since we are dealing with someone who was murdered,' I added.

'Now you're pissing me off,' she said.

'Not intentionally, I assure you.'

'As if someone murdered makes no difference to me? Is that what you're implying? You think I got where I am in life by not giving a shit about who set a fire and why?'

She shoved up her sleeves, as if ready for a fight.

'Teun,' I said. 'I don't have time for this, because I don't think it's constructive.'

'This is about Lucy. You think I'm replacing you, or God knows what. That's what this is all about, isn't it, Kay?'

Now she was making me angry, too.

'You and I have worked together before, right?' she went on. 'We've never had a big problem before now. So one has to ask, what's different? I think the answer's pretty obvious. The difference is that even as we speak, your niece is moving into her new apartment in Philadelphia, to be in my field office, under my supervision. Mine. Not yours. And you don't like it. And guess what else? If I were in your shoes, maybe I wouldn't like it either.'

'It is neither the time nor the place for this discussion,' I said firmly.

'Fine.'

She got up and draped her jacket over her arm.

'Then we'll go somewhere else,' she decided. 'I intend to resolve this before I drive back north.'

For an instant I was stymied as I reigned from the empire of my wrap-around desk, with its foremen of files, and guards demanding the hard labor of journal articles, and legions of messages and correspondence that would never set me free. I took my glasses off and massaged my face. When McGovern was blurred, it was easier for me.

'I'll take you to lunch,' I said. 'If you're willing to hang around three more hours. In the meantime' - I got up from my chair - 'I have bones in a pot that need heating up. You can come with me, if you have a strong stomach.'