We had a plan. Such a good plan. But if there’s one thing I’ve learned in the last few days it’s that plans almost always change.

Lachlan lowers his trendy green-tinted specs and looks at me over the rims with his beautiful second-child eyes. “Ready?” he mouths. My hand goes to the pearls at my throat, and I just barely nod.

As if we choreographed the move for weeks instead of talking about it for a scant few hours, Lachlan lunges at Ash’s face with the pen he’s been twiddling all this time. The guards, probably thinking Lachlan is trying to assassinate their prisoner, reach for the pen . . . but suddenly it isn’t a pen anymore.

At the exact same time, my fingers clench around the short strand of pearls and rip them violently away from my throat. I hurl them to the hard floor and they bounce and roll all around the open room that is lined with cells. Some skip into the entranceway, where more guards are waiting. I see uniformed men and women look down at the innocent-looking little pearls . . . until suddenly they’re not pearls anymore.

I pull my pen that isn’t a pen from my clipboard and press it to my face, where it unrolls itself into a bioadhesive sheet similar to the one in the hazmat suit’s mask. It presses itself to my face, sealing in my eyes, nose, and mouth with just a little gap so I can see and don’t feel like I’m choking. A chemical reaction will give me air for about ten minutes, which should be enough. Through the slight haze of the protective film I can see that Lachlan has his mask on, too.

Then, with a subtle series of pops, the pearls detonate and release their bursts of toxic gas.

I can feel it on my skin, coldness as sharp as if I’d stepped into a freezer. But the drug itself won’t be absorbed through the skin, only through the lungs and eyes. As the guards are beginning to find out.

I remember the smell so well, and I almost wish I could breathe it in one more time. With my new eyes, my new mission, I might never again see that glorious camphor tree that gives the Underground second children hope, happiness . . . and after a little bit of chemical tweaking, an aerosolized plant-based poison capable of taking out a roomful of people.

Nature gives life, and nature gives death. And what are we humans but a part of nature?

It all seems to go perfectly. Lachlan was sure we’d be able to smuggle in the cleverly disguised technology, and he was right. He was certain the camphor-based drug could disable anyone who breathed it in, and he was right. The guards are choking, vomiting, collapsing. Lachlan told me they’ll recover, eventually, but looking at how quickly the guards go from health to misery to stillness, I wonder if he just told me that so I wouldn’t think about having more deaths on my conscience.

In seconds, every guard in our sight is on the ground. This is our moment. We need to run, now, downstairs and out the front door, just three panicked employees fleeing a terrorist attack. We’ll get into the car Lachlan’s people will have stolen and left parked outside the Center, so we can get away as quickly as possible. Within an hour, Ash should be in the Underground, safe.

But there was one thing I didn’t plan for. Beatings, drugging, stress, terror . . . Ash isn’t strong at his best. Now, through the bioadhesive film over his face, I can see the panic in his eyes that heralds one of his attacks. He’s starting to wheeze, his breath a muffled whistle behind the mask. He looks at me in apology for one instant . . . and then his knees buckle.

Our plan relied on a quick exit. Now one of us can’t run.

Lachlan doesn’t hesitate. He strips a jacket from one of the fallen guards and drapes it over Ash, hiding his cuffed hands so that at first glance he looks like a guard, not a prisoner. “Go!” Lachlan shouts, and picks up Ash as if he weighed nothing, slinging him over his shoulders.

We run, out past the fallen guards, to the spiral staircase. The camphor essence makes my exposed skin tingle. Over the railing I can see people on the first floor looking up in alarm.

“Help us!” I shout, my desperate, terrified expression not an act at all as I gesture wildly behind us. “There’s been an attack! They’re all dead!”

I barrel down the stairs and toward the front door. There aren’t as many people as there would be in the daytime, but there are enough to make a panicked crowd, as most run for the exit and a few head up the stairs toward the chaos.

No one seems to notice me. I must look as alarmed and confused as everyone else. But a few are looking suspiciously at Lachlan as he struggles a little bit behind me with Ash over his shoulder. I see a woman point to him, say something to a nearby man. They look around and the woman beckons urgently to someone I can’t see.

Lachlan is slowed by Ash’s weight, and only halfway down the stairs. We’re far enough apart that anyone seeing us wouldn’t think we were together. I want to look at him to call hurry up! But I don’t dare attract more attention. I keep walking slowly across the wide-open lobby toward the door, moving almost sideways, pretending to look up at the commotion on the second floor like almost everyone else is doing.

Then I see who the woman was beckoning to. A Greenshirt appears, heading toward the couple and at the same time scanning the lobby to see what they’re talking about. He has a gun on his belt, but I have no way of knowing if it is the lethal kind.

It doesn’t really matter. Killed or stunned, if we’re hit, we’re done for.

Whatever the people say convinces him. He starts striding across the lobby toward the stairs Lachlan is laboriously trudging down. “Stop right there!” When Lachlan doesn’t react, the Greenshirt starts to run straight for the stairs.

I don’t know what to do. I take a step toward them, not knowing if I’m going to run to help Lachlan and Ash, or attack the Greenshirt. I hesitate too long. I realize I can’t make it to either of them in time. Lachlan is almost at the bottom of the stairs. The Greenshirt is almost on him. His hand goes for his gun.

Then I see the maintenance worker near the pool at the base of the decorative waterfall tumbling from the second to the first floor. She raises her head, meeting my eyes with a quick worried, loving look that somehow reminds me of my mom. My heart seems to dissolve within me, making me weak. I know that look. Mom wore it just before she sacrificed her life for mine.

“No!” I cry out, sure that Lark is going to do something foolishly, fatally, nobly heroic to save us all.

She is. I just underestimate her resourcefulness.

In one swift motion she pulls a heavy wrench from her tool cart and latches it onto a gear in a control panel hidden at the far side of the waterfall. With a grunt of effort, she torques it counterclockwise.