“Novices Fara, Olatji, Kazem, Alasha, Nanjo,” the driver recited tiredly. “Dedicates Egret, Treefrog, Henna, Whitelake. If I may—?”

Crane released the horses, and the wagon rolled on. Rosethorn was shaken and pale. Briar felt as if he’d been dropped down a hole. “Henna was fine when she left to look after the Arsenal setup,” he whispered. “Just fine.”

Rosethorn drew the gods-circle on her chest and closed her eyes to pray. Crane did the same. Briar waited them out as patiently as he could manage. If you give your life to a temple, he supposed, you believed that prayer worked. He knew better.

“Can we get to it?” he asked when they looked up again. “You said there’s things we can do without knowing just how this magic turned into the blue pox?”

“He’s right,” said Rosethorn grimly. “Let’s get to it. That’s the only way we can help them now.”

“Careful,” said Niko. “One more—you’re almost down.”

“And oh, how pleased I am to hear that,” muttered Tris.

“Can we get on with it?” Niko demanded. Tris was feeling for the next rung of the ladder with one foot. Like him, she wore thigh-high boots, oilcloth breeches and robe, an oilcloth cap, mask, and gloves. Like the other workers in Crane’s greenhouse, she also sported a large red dot at the middle of her forehead as a sign she was uninfected with the blue pox. Niko’s red dot, she’d noticed, was on the back of one hand. He never would have consented to an unsightly red mark anywhere on his face.

They had entered the system near Flick’s den, taking the path that Alleypup had used to bring Rosethorn down. Niko had chosen to start where the first case of blue pox had appeared, hoping to trace its path back to its origin.

This time, when Tris put down a foot, there was a small splash and the feel of a hard, flat surface. Wincing, she put her other foot down. Another splat. She released the ladder and turned to scowl at Niko.

Light bloomed around him to reveal a ledge four feet across, spotted with dark puddles. The canal’s waters ran one inch below the ledge. Tris saw lumps carried along by the swift-moving tide and rats that ran squeaking down the ledges, and cringed. The stench flooded through her nose, making her stomach roll. Trembling, she breathed with her mouth open, trying to smell only the oils in the treated cloth of her mask.

“This way,” Rosethorn said. Niko towed her along until they reached Flick’s den. Scavengers had been there already, taking the lamps and whatever else looked to be useful or interesting. Even the bed of rags had been picked over.

Niko removed a glove to rummage in a sack he carried on one shoulder. He produced a small stone jar and opened it. “Take off your spectacles,” he ordered Tris. “Remember the vision-enhancing ointment we made earlier this year?”

“Gum mastic, cinnamon bark and oil, at a silver crescent the ounce, no less!—”

Niko sighed impatiently.

Tris glared at him and continued, “Heliotrope, saffron and cloves, lavender.”

“Very good,” Niko said. “Close your eyes.”

She felt something cool dotted first on one eyelid, then the other. “Wouldn’t it be better put on my specs, the same as your other vision spell?”

Niko sniffed. “That spell wore off a week after I placed it on you.”

Tris donned her spectacles. “You never told me.”

“It slipped my mind,” he replied as he put the balm on his own eyelids, then closed the jar. “There’s an advantage to instructing young mages: a suggestion counts for so much with you four. Now, what do you see?”

Her eyelids tingled. A gold veil dropped over her sight, one that shimmered and caught on objects, then pulled free. It stuck only in a wash through the sewer and on a line of footprints that turned into Flick’s den.

“There’s a gold tint in the water,” she said, watching it. “It comes from upstream. And it’s in footprints too.”

“The tint is throughout the city’s water. It is the footprints we must follow.” Niko walked down the trail. Tris resettled her spectacles on her masked nose—they didn’t fit properly with cloth in the way—and set out after him.

At first they walked in silence, intent on the trail. For some time the prints showed clear through even a slight amount of water. By the time Tris realized that either the ledge was sloping or the water was rising, she was ankle deep. “Oh, no!” she cried. “Niko, stop!”

“What’s the matter?” he demanded.

“We’re walking in it, and it’s getting deeper! You don’t need me for this—please let me go home! Please!”

Niko faced her.

“You see better than I do, and this is disgusting.” Tris knew she was whining and was ashamed, but the horror of soggy lumps that struck her legs in the dark made her dizzy. Never in her life had she wanted to be gone from a place so badly as now.

“Stop acting like a child!” Niko snapped. “This job needs both of us, I explained that to you! Complaining about how dreadful it is only makes things worse, and I don’t need them to be worse. I didn’t ask you to come here lightly, and I would really, really appreciate it if you could just hold your tongue.” He caught his breath and stood still for a moment, eyes closed. After a moment he said, “I hate this too, understand?”

Tris stared at him. Niko was sweating. It was damp and cold here, but she saw drops collect on his forehead. When she tentatively rested a hand on his arm, she could feel him trembling. She had been so busy worrying about herself that she had forgotten how finicky he was. He tended his clothing with minute zeal, inspected tableware in strange eating-shops for dirt that might have escaped a lazy washing, and aired out his bedding the moment he reached a new inn.