The Isle by Jordana Frankel

night, however, I have a surprise.”
    Whatever he’s about to show us . . . it’s good. I can tell. His face is lit up like he’s been plugged into a magic power outlet somewhere. He walks us through the living room and down a narrow, dimly lit hall.
    At a door two rooms down, he stops.
    Seeing what’s inside, I squeak, “They’re glowing!” and run toward what looks like a fish tank. Except, it’s not filled withfish. It’s filled with algae-covered rocks growing neon-green mushrooms. A pump attached brings old water out and circulates it with new water. From underneath, burners heat the tank, throwing off tiny blue circles of fire. “What is this? Is this the water?” It’s all too weird.
    â€œThat’s the water, all right,” Callum says with pride.
    Ren grins. She tousles his already messy brown hair. “You never said you could grow more! Sneaky scientist, ain’t we?” She lets him go and peers down into one of the glass bowls, her finger tracing the rim.
    â€œThat’s because I couldn’t . The mushrooms wouldn’t grow.”
    â€œWhy are the mushrooms so important?” I ask, eyeing their bright green hoods. “I thought it was the water that healed me.”
    â€œIt was. But only because of the mushrooms. They have these chemical compounds, phytonutrients, with medicinal properties, some antitumoral and antiviral in nature. All plants have phytonutrients, actually. Just not in the same quantity or combination. And since the mushrooms grow in an underground hot spring, they release those compounds into the water. That’s how the water cures the Blight.”
    â€œThat, and me ,” Ren quips, pointing a finger at him. She taps the crook of her arm. “My blood. It made the serum work better, naturally.”
    I don’t need to ask what she means: Ren’s immune to the virus. Of course her blood would help. Ren never told anyone about it, though. At the orphanage, Miss Nale warnedher not to. She was afraid the DI would experiment on Ren so badly, she’d end up dead. Which doesn’t seem so far-fetched, now knowing what I do.
    I turn back to the neon tank, mesmerized by the soft green glow. “So how did you keep the mushrooms alive, then?”
    â€œI made a breakthrough,” Callum says with a bounce, clearly happy I asked. “I realized I knew nothing about the cave’s ecosystem. They can’t just grow out of rocks, or water. Plants need soil. In the cave there wouldn’t be soil, but I guessed that there might’ve been some algae growing on the rocks. I tried a few kinds and landed on the right one. Nothing special about the species, but without it, the fungi have no way to grow.”
    â€œSo simple!” I laugh, though I’m sure it sounds much easier than it actually was.
    â€œNot quite,” Callum says, confirming it. “The fungi would seem to be growing, and just when I thought I’d succeeded, they’d die all over again. I was confounded. Until I had my second breakthrough.”
    Ren and I exchange glances, waiting for him to tell us. He leaves us hanging for just a few moments before the big reveal. . . .
    â€œThe fungus is parasitic,” he says at last. “If the spore count grows too large, it will actually kill the algae.”
    Seeing both Ren’s and my blank expression, he explains.
    â€œSpores—they’re like microscopic baby mushrooms. Given the right conditions, they’ll grow. But with too many, the algae dies. No algae, no fungus. That’s why it kept dying off; the spore count would get too high as the fungi reproduced.In the spring’s natural ecosystem—with fresh water flowing in and out—you’ve got a perfect ratio, always in flux.”
    â€œOkay,” Ren admits. “I don’t usually dig the science stuff, but it’s pretty impressive how you just figured all of it