“What’s that, an old MP80?” Cly asked, pointing at the mask.

She bobbed her head. “From the evacuation.”

“It’s a good model,” he observed. “You have any extra charcoal filters for it?”

“No. But these two were never used for long. They should be all right.”

“They’ll be all right for a while. A whole day if you’re lucky. Wait a minute.” He reached under the console and pulled out a carton filled with round discs of assorted sizes. “How big are yours?”

“Two and three-quarters.”

“Yeah, we’ve got some of those. Here, take a few. They’re not very heavy, and they might do you good in a pinch.” He selected four and checked them against one another, and against what light came through the windshield. Satisfied that they were sound, he thumbed them over to Briar. While she inserted them into her satchel, Cly continued. “Now listen, this won’t hold you for the next few days — I don’t have enough to set you up that way. You’re going to have to find some sealed spots with air in them. And they’re down there, I know they are. But I couldn’t tell you how to find them.”

Briar fastened her bag again, knocking the chin of her gas mask on her collarbone when she looked down. “Thank you,” she said. “You’ve been very kind, and I appreciate it. When I’m down there, I mean to go home — I mean, back to my old home, for all that I didn’t live there long. I know where there’s money, real money, and all kinds of… I don’t know. What I’m saying is, I’ll make a point to find some way to repay you.”

“Don’t worry about it,” he said, and his voice was unreadable there inside the mask. “Just stay alive, would you? I’m trying to repay a favor here myself, but I won’t consider it an even score if you go inside and die.”

“I’ll do my best,” she promised. “Now point me to the way out, and let me go find my son.”

“Yes, ma’am,” he said, and pointed back down the steps. “After you.”

It was tough to climb down with the mask knocking against every other rung; and it was hard to see through the round, heavy lenses that cut off all Briar’s peripheral vision. The smell was already driving her mad, but there was nothing to be done about it, so she tried to pretend that she could see just fine, and she could breathe just fine, and that nothing was clenching her head in a viselike grip.

Down in the cargo hold Fang was unlatching the blocks that served as brakes for the big bags on their tracks. Rodimer worked from the other end of the room, gathering the deflated, rubber-treated sacks in his arms and pulling them along the track, drawing them over to the open bay door.

Briar shuffled carefully to the edge of the squared-off hole and peered down into the gas. There was nothing to see, and it shocked her.

The window in the floor revealed a brownish fog that swirled and puffed, obscuring all but the highest building peaks. There was no sign of the streets or blocks below, and no hint of any life except for the occasional caw of a distant black bird with a bitter grudge.

But as she looked longer, Briar saw tiny details here and there, between the briskly stirred clouds. The edges of a totem pole peeked through the gas and vanished. A church’s steeple punctured the ugly fog and was lost.

“I thought you said there were breathing tubes, or…”

And then she saw it. The ship was parked alongside it, so she wouldn’t have seen it by staring down and out, only at an angle. The tube was a bright, cheery yellow and frosted with bird manure. It swayed back and forth, but mostly stayed steady, bolstered by a strange and fragile-looking framework that was fastened around it like a bustle under a skirt. Briar couldn’t see what this framework was fastened to, but it was secured against something under the clouds of fog — perhaps rooftops, or the remains of trees.

The tube’s exit end was lifted up above the tainted air. It was big enough to accommodate Briar and possibly a second person at the same time.

She craned her neck to see it, trying to find the top.

“We’ve still got to rise a little,” Cly said. “Give it a minute. We’ll climb another few feet, and then we’ll be close enough for you to dive. The gas is dense. It’ll push us up a little farther before we load.”

“‘Dive,’ ” she repeated, trying not to choke.

The world was spinning beneath her, bleak, blind, and bottomless. And somewhere, hidden within it, her fifteen-year-old son was lost and trapped, and there was no one to go down there and get him except for his mother. But she had every intention of finding him, and hauling him out on the Free Crow in three days’ time.

Focusing on. this goal and swearing that it was a strict eventuality did little to calm the throbbing horror of her heart.

“Having second thoughts?” Rodimer asked. Even through his gas mask Briar thought she heard a note of hope in the question.

“No. There’s no one else to get him. He doesn’t have anyone else.” But she couldn’t tear her eyes away from the murky vortex beneath the ship.

As the Naamah Darling rose, pushed above the gas foot by foot, the air tube came into clearer focus. From the greater height Briar could see hints of other tubes jabbing up through the disgusting cloud. They waved like the antennae of giant insects hiding in the haze, pinned together with sticks and slowly bobbing against the nasty currents, but remaining always upright.

And then they were above the lip of the tube, just barely — just enough that Briar could grab it. She reached out a hand, down through the open bay, and she wrapped her fingers around the edge.

The tube felt rough to the touch, but strangely slick. Briar thought it might be burlap coated with wax, but through the thick lenses of the mask she couldn’t see well enough to guess any better. The tube was ribbed with hoops of wood to keep its shape, and these ribs bulged at four-foot intervals, giving the tube the appearance of a segmented worm.

Finally the ship was as high as it was going to get, and the tube’s mouth was just beneath it.

The captain said, “Now or never, Miss Wilkes.”

She took a deep breath, and it hurt — drawing the air, forcing it past the filters and into her chest. “Thank you,” she told him again.

“Don’t forget: When you get over the side, spread out to slow your way down.”

“I won’t forget,” she said. She tossed a parting nod at Rodimer and Fang both, and grasped the tube’s edge.

Cly walked around the square bay door. He twisted his wrist in a cargo net and used it to hold himself steady. “Go on,” he told her. “I’ve got you.”

Although he wasn’t touching her, she could feel him there behind her, arms out, unwilling to let her fall where she shouldn’t. Then his free arm swung to hold her elbow.

She leaned against him while she lifted her leg and sent it over the lip of the tube. With a short lurch she left the Naamah Darling and the support of the helpful captain and fell a few feet until she was straddling the tube’s wall. Briar snapped her arms and legs tight around it, clinging to it tightly.

She closed her eyes, but opened them again, because it was better to see even if the view nauseated her. The tube was not as steady as it seemed, and it dipped, weaved, and bobbed. Even though the motions were slow, they were impossibly high above the earth. Every fraction of an inch one way or another was enough to take her breath away.

Over on the Naamah Darling, three curious faces peered out through the bay.

They were still close enough, and the captain was long-limbed enough, that if she were to reach out and beg, they could pull her back on board. The temptation was almost more than she could stand.

Instead, one shaking finger at a time, she peeled her death grip free of the tube and sat up enough to pivot her hips and bring her second leg over the edge. She paused there for a moment, as if she were entering a bathtub. Then, with one last look over her shoulder — too quick to change her mind — she pitched forward into the deep black interior of the fresh air apparatus.