But if you're trying to see whether the influence of, say, Beelzebub is leaking out of a toxic spell dump, you don't go about summoning up Beelzebub to see if the law of similarity applies - not if you're in your right mind, you don't, anyhow. Byproducts from spells that invoke Beelzebub are contained within warded dumps for good reason: you don't want them getting out into the environment And if you summon the Lord of the Flies outside the containment area, that's just what's going to happen.

And so Michael Manstein attacked the problem indirectly.

I mention Beelzebub because that's Whose influence he was checking for when Tony Sudakis and I came back from our sub rosa (or should I say sub sucino?) chat Instead of even thinking about invoking the demon, he pulled out a jar full of every thaumaturge's friend, the good old common fruit fly.

Because fruit flies are very simple - and very stupid - creatures, they're exceptionally sensitive to mage.

Apprentices practice spells with them; if you can't make your charms work on fruit flies, you're better off in another line of work.

And when that magic has anything to do with Beelzebub, of course, their sensitivity increases even more. Just by watching the way they flew from the jar, Michael could tell whether the demon's influence had leaked out where it didn't belong. It was as elegant and low-risk a test as you could imagine.

Since I'm not a mage myself, to me that just looked like little brownish flies coming out of a bottle. When Michael screwed the lid back on, I figured I could safely interrupt him, so I asked, "Any skin of Beelzebub?"

"None apparent to me," he answered. The Lord of the Flies is renowned for his trickery, but I do not believe him capable of evading the fruit-fly test; it draws them even more strongly than spoiled plums."

"Good to hear," I said, "because I know there are spell byproducts with his influence on them inside the dump."

"Yes, that is to a certain degree reassuring," Michael agreed. "If a Power so corrosive as Beelzebub cannot break free of the containment area, that augues well for its chances of holding in other, less aggressive, toxic spells."

"Who after Beelzebub?" I asked.

"I had thought Huitzilopochdi," he answered. "He is at least as dangerous as Beelzebub, and we have seen through the case of that wretched curandero's nostrum that he is active - and seeking to become more active - in the Angels City area."

Again, he didn't try to invoke the Aztedan war god: after all, we were doing everything we could to keep Huitzilopochdi from manifesting himself around Angels City. Instead, he performed another indirect test, this one using flayed human skin substitute. It looked like parchment, but it made my flesh creep all the same.

Michael chanted hi a clucking, gobbling language. It wasn't Poultry; it was Nahuad. Spainish is the dominant tongue in Aztecia today, but many people still use Nahuad in their day-to-day lives, and it's as much the language of the native Powers as Arabic is forjinni. I hadn't known Michael knew it, but I wouldn't bet against Michael's knowing any particular tiling.

The chant ended. Michael looked down at the square of flayed human skin substitute. It seemed just the same as it had when he took it out of his bag. He grunted softly.

"What's the matter?" I asked.

"I would have expected to observe some reaction there," he answered. "Huitzilopochdic contamination is as likely an inducer of apsychia as any I can think of. But there appears to be no external seepage, at least not as measured by this test."

"What were you expecting to see?" I asked.

"The influence of Huitzilopochdi was brought into the Devonshire toxic spell containment area by means of flayed human skin substitute. Had that influence spread beyond the containment area, the sheet of the substitute material I have here would have demonstrated it by beginning to bleed."

I gulped; I was sorry I'd asked. "Would it be - real blood?" I asked.

"In diaumaturgy, 'real' is a word almost witthout meaning," Michael said sniffily. "It would look, feel, smell, and taste real. Whedier it could be successfully removed from the flayed human skin substitute and impplanted in the veins of someone who had suffered a loss from injury or vampirism… Truth to tell, I do not know. It might be worth determining. An interesting question. Yes."

He pulled a pencil out of the pocket of his lab robe, peered around for something on which he could jot a note.

For one dreadful second, I feared he was going to scribble on the piece of flayed human skin substitute. I don't think my stomach could have stood that. But at the last minute he fished out a parchment notebook instead, and did his jotting on that.

He spent the rest of the morning and the whole afternoon on tests of that sort. To my amazement and distress, he came up empty every time. No, I take that back: he did find one leak. After four in the afternoon, when both of us were fed up and frustrated enough to try something silly, he tested for stardust, and sure enough, the tip of the wand he was using glowed for a minute.

"Undoubtedly deposited here, along with more unsavory items, by one of the Hollywood light-and-magic outfits in search of a hit," Michael said.

"But even if stardust is leaking, it's not toxic," I said. "The most it could possibly do would be to make somebody popular who doesn't deserve to be."

Michael Manstein looked at me as if I were a schoolboy who'd added two and two and come up with three. Not five, but definitely three - I'd fallen short of what was expected of me. Like a good schoolmaster, he set me straight: "The problem is not stardust outside the containment area, David. As you say, that is trivial in and of itself. The problem is that stardust could not possibly get out of the dump if it were not leaking. We have, therefore, established that the leak exists.

What we have not established is which serious contaminants are emerging from it."

"Oh," I said, feeling dumb. Odds were awfully good that he was right. Still, though - "You tested for all the dangerous Powers whose influences are likely to be in the dump, and came up with zip. Stardust is pretty elusive stuff; even the light-and-magic people don't know for sure where it'll stick. Maybe it did leak out by itself."

"Indeed," Michael said. "And maybe you could find a mineral able to create blasts to rival those of megasalamanders, yet I would not lose sleep fretting over the probability of either event. I will take oath upon any scripture you care to select that something - and something malevolent, at that - created the breach through which the stardust emerged. That is my professional judgment."

You work with experts to get their professional judgment.

If, having got it, you then choose to ignore it, you'd better have a real good reason. I not only didn't have a real good reason, I thought Michael was right. But if he was, what had gone wrong? 

I said, "What bothers me most about detecting the stardust and nothing more serious is that the dump operators will be able to claim that the dust didn't really come from inside, even though we know it was dumped there."

"The neighborhood will make it hard for them to substantiate that." Michael waved to show what he meant I had to nod. If ever a neighborhood remained conspicuously untouched by stardust, the one around the Devonshire dump was it "Why haven't we found any nastier influences leaking, then?" I asked.

The most obvious reason is a failure in our testing technique," Michael answered. "I must confess, however, that at this moment I cannot tell you where the flaw lies. All my procedures have in the past shown themselves to be more than satisfactory."

I asked my watch what time it was. When I found out it was twenty to five, I said, "Let's knock off for the day and see if we're more brilliant in the morning." I wanted to get back to my own carpet so I could go down to my place, pack an overnight case, and then head for Judy's.