Valko jumping out at that column of shadow and barking as loud as he could ( pretty good , thought Maya, for his third bark ever ); the shadow almost losing its balanceâif losing its balance is something a whirling column of dust can doâfalling back, straightening up again, stretching tendrils of darknessâ arms âout in front of itself, reaching, reaching past Valko, feeling for something else or someone elseâ
Then . . .
M a y a , it said, in exactly the sort of ghastly dry whisper a column of leaves and dust would use if it was trying to learn to speak.
They turned and ran.
It wasnât far to the end of the street. At the corner Maya took a chance and looked back.
âHey, wait,â she said, panting hard. âLook at that.â
The shadow seemed to be stuck a ways behind them. They could see it pushing against the air, almost as if it had hit a wall.
âStay here,â said Valko, and he walked back a bit to look. He always had to investigate things properly. Maya shifted her weight from one foot to the other. Her feet were eager to keep moving.
âThe airâs different here,â Valko called back over his shoulder. âNotice that?â
He was keeping his eyes glued to that shadow, though.
Maya took an exploratory breath. The air was different. It was like something chaotic in it had vanished. The hum was gone.
She saw Valko take another few steps and then pause. The sackâs worth of shadow pressed against that invisible wall, but the wall didnât yield.
He went closer. The shadow just eddied there, waiting.
âCareful,â said Maya.
âDonât worry,â said Valko. He crossed over to the other side of the street. The shadow stayed where it was. It didnât seem to notice Valko coming closer from the side; Maya could have sworn it had its nonexistent eyes fixed entirely on her. Not such a good feeling.
âItâs like thereâs a shimmer in the air here,â said Valko. âLike an edge in the air. Or a wall. Do you see it? Look, I can just slip my hand right throughââ
âEep!â said Maya. It came out more as a sound than a word.
âI know,â said Valko, without turning around. âI saw that, too.â
When Valkoâs hand had gone past that edge, the shadow thing had moved a little ( turned its head , suggested Mayaâs mind, ignoring for a moment the point that columns of shadowy dust donât actually have heads). That was creepy.
A biologist who has just run into a grizzly bear will move with great caution; so did Valko. He seemed to be carefully fishing something out of his pockets. Maya squinted: oh, a pencil. Was he going to stop to take notes ? How completely crazy could one person even be? She walked a few paces in his direction, just in case she needed to grab him by the sleeve and haul him away.
But now Valko was running his hand across the wall, right to the very place where the shimmer started.
âUm, what are you doing?â said Maya, trying not to catch the shadowâs attention. âSeems like we should just leave, doesnât it?â
Valko was making a careful line of X s right there.
âMarking the edge,â he said. âGot to be dark enough to find later, but not so big the graffiti police come and wipe it off.â
M a y a , said the shadow thing.
âEnough,â said Maya, shuddering slightly.
âDefinitely enough,â said Valko, stuffing the pencil into his pocket. Maya and Valko trotted back to the far end of the alleyway, and then one block farther from the river, because Valko wanted to see if they could see a boundary there, too.
They could. Valko ran down that street to the very edge of the shimmering air and left some more X s on that wall, too.
It was five long minutes before the shadow appeared in that street, so at least (said Valko to Maya) it was dumb and slow .
âDumb, slow dust thatâs walking and