"Hello, Doc." Storm stops in front of an excavation site bounded on four sides with planks of wood that the doc will pack up and take with her to keep from being stolen. Beside the hole, the doctor has set up a makeshift lab: a few beakers and vials of solution beside a field microscope.

Doc Raines rattles her curls impatiently. "Look," she says without preamble, pointing to her makeshift lab. Storm hitches up the leg of his monstrously expensive trousers and bends down beside her. We watch as she pours the contents of one beaker into another. She takes a pipette with a dirt-smudged tip and drops something into the beaker. She stirs once, twice. Something happens; the formerly clear liquid turns a cloudy red.

The doc turns to Storm with a sharp, expectant look.

"You're going to have to draw us a picture, Dorian," drawls Storm.

"I've been shipping the samples back to my lab and having the damnedest time getting a read on anything. With each sample test, the roots were inert. Like looking at rock. Which didn't make any sense, since they're roots. At the very least, there should be evidence of organic decomposition, if not some trace of chemicals or just—something."

The doctor grabs at Storm's hand, something I've never seen her do before. Doc Raines doesn't do touching, unless it's to heal. She turns to us with a beaker filled with clear liquid. She throws in a pipette of dirt. Even before she begins to stir it, the liquid turns stormy and red.

"I'm using a biosensor assay. In the presence of active nanoparticles, it changes color. The more active the nanoparticles, the faster and more complete the color change." She looks around, eyes lit with fear and wonder. "Do you understand what I'm saying? It's full of nanotech."

"Does it test for any particular kind of nano, Dorian?"

"The kind that targets biological agents. It must be loaded with some variation of a growth factor I've never seen before," the doctor replies with a wry smile. "My guess is, once the organic compounds begin to die, the nanotech is programmed to self-destruct, leaving no trace of its existence or the organic composition it was targeted to."

"Which is why you can't find it in your lab."

The doc nods at Storm like he's been a star pupil. "Which is why I can't find it in my lab."

I stare at the vial in her hand, the bright-red color fading as the technology kills its host. "What the hell made that?"

We stay at the Prayer Tree for hours, culling samples from different areas of the root system and the bark, and subjecting it to the same test. The results are always the same: The clear liquid turns a deep, rich red in an instant. At one point the doctor calls over Mohawk to help her jerry-rig a tent over her makeshift lab. Maybe it's the rain, zigzagging down in a wet blanket, that makes the streets so eerie. Or maybe it's that we don't see or hear a single soul. I keep half an eye out anyway, waiting for the urchins from the kid gangs to make an appearance, and especially the little girl I met the other day. I'd hoped she'd be looking for more food.

No one shows.

If it weren't for the new graffiti on the walls, now bleeding down in rich crimson streaks, and the jingling tokens newly left in the branches since our last visit to the tree, I'd have said the city was empty.

It must be ten minutes later that I catch a slight movement, quick and light as a bird, from the corner of my eye. I swivel my head, hoping to catch whatever it is, but it disappears. Feeling eyes on my back, I turn toward the tree and Doc Raines, who continues to school Storm on DNA-based nanotech. There—again. Just to my right, around the side of the building colored over with the largest set of circles.

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