“Okay, gotta go, gotta go,” Winnie chanted, dragging him forward by the arm. They ducked into the corner formed by a wall and a dead end, and plastered themselves to the wall. Seconds later, the entire world bucked around them as, right where they had been standing, a large metal ball rocketed past.

It was like the boulder scene from that old Indiana Jones movie. Except there was no way to outrun this thing.

“Wow,” Ahmad gasped. “Where did that come from?”

Winnie panted beside him. “I have no clue, but I’m just glad we didn’t spin away with it.”

Ahmad couldn’t respond because something else had drawn his attention. Now that the ball was rolling off in the distance, that hum had broken through above everything else. As a matter of fact, it wasn’t really a hum anymore. There was a steady plop, plop, plop.

It was like a running faucet.

Or a broken dam.

Ahmad rushed back into the corridor and stopped. Where the ball had rolled, it had shifted the sand spread underneath, revealing shimmering blue tiles. He held his shoe experimentally over the nearest one before lowering it down. As it settled, slight ripples moved backward from the heel.

“It’s some sort of artificial river,” Winnie whispered in awe.

“Yeah, but why?”

There was a glimmer beneath Ahmad’s toes. He gasped and reared back. Where his shoe had been, a beautiful golden koi swam forward. As the kids watched in awe, it leapt up—right out of the tile, hovering in midair and catching purple light off its scales—before it landed in the next tile and vanished.

“How did it do that?” Winnie asked, but Ahmad had focused on something else entirely.

“Did you see that mark on its back? It looked like a key. The key! That’s what we need to get. Come on!”

“Ahmad! Hey, Ahmad, wait!”

But Ahmad was already bounding off in hot pursuit. He didn’t get too far, though. One wrong step, and his foot had landed on one of the water tiles.

Well, it didn’t land. It went right through it.

“Cold, cold, cold!” Ahmad yelped. He yanked his leg upward, eyeing it suspiciously. Transparent droplets beaded up against his jeans and vanished without leaving any dampness.

“That is freaky!” Winnie said, catching her breath beside him. “Either way, now we know for sure we can’t walk on water. It’s the unbroken tiles for us.”

“Okay, fine, but we need to keep up with that fish,” Ahmad insisted. After giving his leg one final shake, he raced forward again. Shaking her head, Winnie followed.

“So just how are we going to catch that thing?” Winnie called as they hopped from tile to tile, pausing every so often as the ground trembled beneath their feet. “I don’t think using our hands will work.”