Suddenly the trail ended in a broad, drippy blotch in the center of the tunnel and along a curved wall. Niko and Tris looked up. Immediately above that gold blotch was a barred rectangle of light: a grating. They could hear the rattle of wheels on cobblestones and a distant clock striking the half hour.

They had passed ladders to the street all during their expedition. There was one five yards ahead with a sign next to it that read LUCKY STREET & SHORTSHANK WAY. Niko climbed up, opened the exit and looked around, then sank down a rung. “Stand back,” he ordered Tris.

Confused, she did as she was told. Niko stripped off his heavy outer garments, dropping them into the sewer: only his mask, gloves, and street clothes remained. He then boosted himself up onto the street. “You do the same,” he ordered, his voice a haunting drift from the light overhead. “Wait until you’re almost out.”

“Oh, joy,” she muttered, panting as she struggled to climb the ladder. She tried not to remember that her three housemates would have clambered up like monkeys.

When Tris emerged, blinking, into the light, Niko stopped her. He’d removed his gloves and tossed them into the sewer. Now he pulled fresh ones from his satchel, giving a pair to Tris. As he placed the cover on the sewer hole, she looked around. They were not in the best part of town. Houses were jammed together, cobbles broken or missing in the street. A view of a towering wall between her and the sun told her they were in East District, near the wall that separated the poorest part of Summersea from the Mire.

Bodies lay on either side of the narrow rising way, many attended by rats. What faces she saw were covered with blue spots. Far down Lucky Street she heard a clanking sound, metal-shod wheels on stone. A wide, deep-bedded dray made its slow way uphill toward her. Workers in gloves, robes, and masks loaded the dead into it.

Those few who walked the hilly streets abroad were veiled or masked and moved with a quick, scuttling gait not unlike that of the rats. If they were puzzled at the emergence of a man and a chubby girl from the sewer, they kept it to themselves. Blue circles were painted on a number of doors to mark where the disease had struck. Fires burned on the corners. Homeless animals, their owners dead, roamed everywhere, digging through garbage in the hope of finding a meal.

A bony hand rested on her shoulder. “You can’t think of that,” Niko said. Of course he’d seen her eyes fill at the sight of the starving creatures. “We have to track down the disease. Time to renew the balm.” He fished out the jar and, taking off a glove, dotted Tris’s eyelids and his own. “Don’t put your spectacles on just yet. Since we now trace not the magic as it became the plague, but the magic alone …”

He drew a glass vial from his satchel and opened it. As Niko touched the bottle’s damp stopper to her eyelids and to the center of her forehead, above the diagnosis oil, Tris’s long nose twitched. New scents—heavy, unpleasant, musty—poured into that sensitive organ. She was about to inquire when Niko said quickly, “You won’t learn what goes into this one for a couple of years—some of the ingredients are poisonous. Don’t even bother to ask. You can put your spectacles on.”

She blinked as vapors from the new liquid made her eyes sting. While Niko anointed his lids—she saw them blaze with her changed vision—she looked around. Scraps of magic glinted in corners and on door and windowsills, the remnants of luck and prosperity charms, love potions, and other small workings. A thin, blue-white cord stretched from a nearby sewer grating up the street.

Niko beckoned her; they followed the blue-white cord to a tall, ramshackle house nearby. The door, a blue circle painted around the knocker, was half off its hinges, which made it easy for Tris and Niko to enter. They stood in a dark and narrow hall, ankle deep in trash, facing a rickety staircase. All the doors on this story were as useless as the front door. Rats and insects fled into the empty rooms, trying to escape the light that now shone bright around Niko.

The blue-white cord led them up three flights of stairs. Tris guessed that this place had rented out rooms. It seemed that now most, if not all, of the building had been abandoned in the wake of the blue pox.

The staircase ended in a garret. The looters had apparently ignored this level. Maybe they don’t like stairs either, thought Tris as she fought to catch her breath. There were only two apartments: the cord vanished through the closed door on one. Niko rapped hard, then tried the knob, only to find it locked. He sighed.

“We should have brought a guard with us,” he told Tris. “Now I have to find one—why are you smirking at me?”

Tris drew a small, rolled-up cloth from her pocket. Briar? she called through their magical bond. I need some advice.

Briar was about to pick up a new tray. Now he stepped away from the stack and turned his attention to his friend. You came to the right person, he said with approval, inspecting the locked door through her eyes. Smart thinking, to bring your picks. That winter, in exchange for lessons in reading classic Kurchali, he had begun to teach her the art of lock picking. Which pick do you need to start?

The long, straight one? she replied, a bit unsure.

Good. Now, get close.

Tris knelt before the lock and let Briar help her through the rough spots as Niko watched, bemused. She only needed two picks before the lock gave and the door opened. A wave of rot-stench surged from the room inside.

“Someone died here,” Niko remarked.

“If you hadn’t told me, I might never have known.” Tris’s sarcasm was nearly lost in the croaking of her voice as she swallowed a mouthful of bile.