By now the skull had been opened, the rubbery, fire-shrunken brain sectioned and still on the cutting board.

'In the first place,' I answered, 'nothing is going to be helpful postmortem because the brain is cooked. But even if that were not the case, looking for a morphological correlate to a particular psychiatric syndrome is, in most cases, still theoretical. A widening of the sulci, for example, and reduced gray matter due to atrophy might be a signpost if we knew what the weight of the brain originally was when she was healthy. Then maybe I could say, Okay, her brain weighs a hundred grams less now than it did, so she might have been suffering from some sort of mental disease. Unless she has a lesion or old head injury that might suggest a problem, the answer to your question is no, I can't tell.'

McGovern was silent, and it was not lost on her that I was clinical and not the least bit friendly. Even though I was aware of my rather brittle demeanor around her, I could not seem to soften it. I looked around for Ruffin. He was at the first dissecting sink, suturing a Y incision in long strokes of needle and twine. I motioned to him and walked over. He was too young to worry about turning thirty anytime soon, and had gotten his training in an O.R. and a funeral home.

'Chuck, if you can finish up here and put her back in the fridge,' I said to him.

'Yes, ma'am.'

He returned to his station to finish his present task while I peeled off gloves and dropped them and my mask into one of many red biological hazard containers scattered around the autopsy room.

'Let's go to my office and have a cup of coffee,' I suggested to McGovern in an attempt to be a little more civil. 'And we can finish this discussion.'

In the locker room, we washed with antibacterial soap and I got dressed. I had questions for McGovern, but in truth, I was curious about her, too.

'Getting back to the possibility of drug-induced mental illness,' McGovern said as we followed the corridor. 'Many of these people self-destruct, right?'

'In one way or another.'

'They die in accidents, commit suicide, and that gets us back to the big question,' she said. 'Is that what happened here? Possible she was whacked out and committed suicide?'

'All I know is, she has injury that was inflicted before death,' I pointed out again.

'But that could be self-inflicted if she were not in her right mind,' McGovern said. 'God knows the kinds of self-mutilation we've seen when people are psychotic.'

This was true. I had worked cases in which people had cut their own throats, or stabbed themselves in the chest, or amputated their limbs; or shot themselves in their sexual organs, or walked into a river to drown. Not to mention leaps from high places and self-immolations. The list of horrendous things people did to themselves was much too long, and whenever I thought I'd seen it all, something new and awful was rolled into our bay.

The phone was ringing as I unlocked my office, and I grabbed it just in time.

'Scarpetta,' I said.

'I've got some results for you,' said Tim Cooper, the toxicologist. 'Ethanol, methanol, isopropanol, and acetone are zero. Carbon monoxide is less than seven percent. I'll keep working on the other screens.'

'Thanks. What would I do without you?' I said.

I looked at McGovern as I hung up, and I told her what Cooper had just said.

'She was dead before the fire,' I explained, 'her cause of death exsanguination and asphyxia due to aspiration of blood due to acute neck injury. As for manner, I'm pending that until further investigation, but I think we should work this as a homicide. In the meantime, we need to get her identified, and I'll do what I can to get started on that.'

'I guess I'm supposed to imagine that this woman torched the place and maybe cut her own throat before the fire got her first?' she said as anger flickered.

I did not answer as I measured coffee for the coffeemaker on a nearby countertop.

'Don't you think that's rather far-fetched?' she went on.

I poured in bottled water and pressed a button.

'Kay, no one's going to want to hear homicide,' she said. 'Because of Kenneth Sparkes and what all of this may imply. I hope you realize what you're up against.'

'And what ATF is up against,' I said, sitting across my hopelessly piled desk from her.

'Look, I don't care who he is,' she replied. 'I do every job like I fully intend to make an arrest. I'm not the one who has to deal with the politics around here.'

But my mind wasn't on the media or Sparkes right now. I was thinking that this case disturbed me at a deeper level and in ways I could not fathom.

'How much longer will your guys be at the scene?' I asked her.

'Another day. Two at the most,' she said. 'Sparkes has supplied us and the insurance company with what was inside his house, and just the antique furniture and old wood flooring and paneling alone were a massive fuel load.'

'What about the master bath?' I asked. 'Saying this was the point of origin.'

She hesitated. 'Obviously, that's the problem.'

'Right. If an accelerant wasn't used, or at least not a petroleum distillate, then how?'

'The guys are beating their brains out,' she said, and she was frustrated. 'And so am I. If I try to predict how much energy would be needed in that room for a flashover condition, the fuel load isn't there. According to Sparkes, there was nothing but a throw rug and towels. Cabinets and fixtures were customized brushed steel. The shower had a glass door, the window had sheer curtains.'

She paused as the coffeemaker gurgled.

'So what are we talking about?' she went on. 'Five, six hundred kilowatts total for a ten-by-fifteen foot room? Clearly, there are other variables. Such as how much air was flowing through the doorway…'

'What about the rest of the house? You just said there was a big fuel load there, right?'

'We're only concerned with one room, Kay. And that's the room of origin. Without an origin, the rest of the fuel load doesn't matter.'

'I see.'

'I know a flame was impinged on the ceiling in that bathroom, and I know how high that flame had to be and how many kilowatts of energy were needed for flashover. And a throw rug and maybe some towels and curtains couldn't even come close to causing something like that.'

I knew her engineering equations were pristinely mathematical, and I did not doubt anything she was saying. But it did not matter. I was still left with the same problem. I had reason to believe that we were dealing with a homicide and that when the fire started, the victim's body was inside the master bath, with its noncombustible marble floors, large mirrors, and steel. Indeed, she may have been in the tub.

'What about the open skylight?' I asked McGovern. 'Does that fit with your theory?'

'It could. Because once again, the flames had to be high enough to break the glass, and then heat would have vented through the opening like a chimney. Every fire has its own personality, but certain behaviors are always the same because they conform to the laws of physics.'

'I understand.'

'There are four stages,' she went on, as if I knew nothing. 'First is the fire plume, or column of hot gases, flames, and smoke rising from the fire. That would have been the case, let's say, if the throw rug in the bathroom had ignited. The higher above the flame the gases rise, the cooler and denser they become. They mix with combustion by-products, and the hot gases now begin to fall, and the cycle repeats itself creating turbulent smoke that spreads horizontally. What should have happened next was this hot smoky layer would have continued to descend until it found an opening for ventilation - in this case, we'll assume the bathroom doorway. Next, the smoky layer flows out of the opening while fresh air flows in. If there's enough oxygen, the temperature at the ceiling's going to go up to more than six hundred degrees Celsius, and boom, we have flashover, or a fully developed fire.'