THE APOTH TOWER WAS abuzz with officers as I ran up the steps. The Legionnaires cleared the way for me, ordering folk to step aside, and soon I was back in Nusis’s office, the walls stacked with tanks and jars and pots, the throngs of worms writhing behind so many glass walls, though now all was shadowy and silent, and the air reeked with the copperish scent of blood.

“Come in, Din,” said Ana’s voice from the far darkness. “I need you to see for me.”

I took a lantern from a Legionnaire and moved closer. Ana sat before Nusis’s desk, I saw, blindfolded, head bowed. Sitting behind the desk was Nusis.

She was bent forward, her head resting on the desk with her arms on either side like she’d been working and decided to take a short nap. Spreading from the base of her neck was a pool of blood, smooth and dark and mirrorlike. It dripped off the edge with a slow pat-pat.

I could not see her face. For that, I found myself glad.

“No,” I murmured. “No, I…It can’t truly be her, can it?”

“Din,” said Ana. “Focus. The base of the skull. Please look.”

Trembling, I walked around the corner of the desk. Her hair was thick and took some work to part; but there, behind Nusis’s ear, was a small, dark purplish hole, slowly leaking blood.

“The Hazas’ twitch?” I asked. “They…they did this?”

“The wound looks the same as the others?” Ana said sharply. “Not a mimicry? Because, if so…Then yes. I believe it is the work of the twitch. Are there any other injuries upon her?”

“No, ma’am. None that I can see. But…why would the twitch bother with Nusis?”

Ana cocked her head. “Can you confirm if her safe is still locked?”

I confirmed it was, the front sealed tight. “It is, ma’am.”

“Is there any blood upon the safe?”

I studied it in the lamplight. “No, ma’am.”

“Hm. Any aroma to it?”

I leaned close, sniffing the air. “There is, ma’am. Alcohol, I think. Just a hint of it.”

“Good. We shall confirm more when the trackers arrive…”

“Trackers?”

Three Apoths then strode through the office door, their movements confident and assured. I recognized them immediately: Princeps Kitlan and the two trackers from the contagion crew that we’d ridden out with.

The three Apoths looked at the corpse with blank, hard eyes, then bowed to Ana. “You called for us, ma’am?” asked Kitlan.

“I did,” said Ana. “This, obviously, is a death scene, Princeps, and we’ve need of your talents. I was wondering if you could catch any additional aromas about this place—and possibly remove the door to Nusis’s safe. I believe you lot are in possession of some rather advanced corrosives…”

“We are, ma’am,” said Kitlan. “Mostly for destroying contagion. But we’d be happy to comply here.” She waved to her tracker, who moved to the door of the safe and slid his pack off his back.

He sniffed the door of the safe as he sat before it. “Smells of alcohol, ma’am. Grain, I think. Probably from the immunis’s own stores. But…it also smells of blood.”

“Blood?” asked Ana.

“Yes, ma’am.” He nodded at Nusis. “Her blood.”

“You’re sure?”

“I am. I’ve enough here to sniff to make a match. It’s the same. My guess is the safe was bloodied, and then cleaned with alcohols.”

Ana steepled her fingers. “I see…Would it be safe to say, then, that the killer manipulated or touched the safe after killing Nusis? With bloodied hands? They likely did not kill her beforehand, since, well, Nusis couldn’t open her safe if she was dead…”

The tracker shrugged. “Seems likely, ma’am.”

“I see. Then please remove the door.”

Kitlan and the tracker carefully applied drops of some smoking black reagent to the hinges of the safe. They did so in several rounds, tugging at the door after each application, until finally there was a groan, and the door fell away.

“Now, Din,” said Ana. “Look. Remember. Has anything within the safe been stolen? Anything missing?”

I squatted to look, my eyes shivering as I summoned up my memories of the last time I’d glimpsed inside this safe. I saw the boxes of grafts, a handful of papers I had seen before; and there, in the corner, the reagents key I’d brought to her, the vial set in a little bronze disc. Everything was all still here—or so it seemed.

“The key, Din,” said Ana. “Is the key there?”

I peered at the reagents key, then gestured to the tracker to hold the mai-lantern close.

“Well?” demanded Ana.

“There’s…a key, ma’am,” I said slowly.

“But?”

I peered closer at it. “But…it’s not the key I got from Aristan’s safe house, I think.”

A thunderstruck silence.

“What?” said Ana.

I turned to the tracker. “Can I pick it up, you think?”

The tracker leaned forward and sniffed the safe. “Not catching scent of any graft trips…though the scent of blood and alcohol is much stronger in here.”

“The killer cleaned the interior of the safe, you mean?” said Ana.

“Seems likely, ma’am. But it should be safe to review.”

I lifted the reagents key, held it up next to the lantern, and studied it. I shook my head. “I’m sure, ma’am. It’s not the same key. The bronze of the disc is discolored in the wrong places. And it’s missing a few dents. There were four total, one big, three small. And the weight is wrong.”

“You remember all that?” asked the tracker, surprised.

Kitlan snorted. “Boy’s an engraver. That’s what he’s here for.”

“You’re sure about all this, Din?” asked Ana.

I felt the tickling in my eyes as I recalled it. “I’m sure of it, ma’am. This key is similar—but it’s definitely different.”

“Can we figure out what this new key is, then?” she asked.

The tracker took the key from me and sniffed it. “Well, it’s…it’s a reagents key, ma’am. I can smell it. Smelled ’em before. Dunno what kind, though, or what portal it opens, but…I do note it smells very, very strongly of blood as well, though it’s also been cleaned.”

“But you’re sure it’s a reagents key?” asked Ana. “An ordinary one? Nothing special about it?”

“Nothing that I can tell. A reagents key, ordinary enough.”

Ana was silent for a long time.

“What’s going on, ma’am?” I asked. “Why kill Nusis?”

She said softly, “Take me back to the Iudex tower, Din. Now. Quickly.”

---

—

WE CROSSED THE city together, the moon pale and sickly above us, the city full dark except for the lamp of the Legionnaire accompanying us several span ahead.

“What do you think happened back there, ma’am?” I asked.

“Evil,” whispered Ana, “and trickery. I think the twitch came looking to steal the reagents key you found in Aristan’s safe house. Yet they were in for a surprise…for after killing Nusis, they found that the key had already been stolen, with another key left behind—a fake. The one you just handled.”

“What?” I said, stunned. “You think tha—”

“Keep your voice down!” she hissed. “It’s now clear that there are many spies among the Iyalets here! I cannot give the game away just yet.”

I whispered, “Do…do you really think so, ma’am? That there’s a…what, a thief about?”

“I do. Someone must have learned what Nusis had in her safe, snuck in, opened her safe, and took it, leaving another key in its place. Then the twitch came, forced Nusis to open her safe, then killed her…yet when they seized their treasure, they realized it wasn’t the right key. Someone had beaten them to it. The twitch then understood they were in a tricky spot—robbed of their prize, and now fearful we might now realize the true nature of the thing they sought. So they carefully shut the door and wiped it with alcohol, removing any blood, hoping we might not deduce what could have been worth murdering and robbing poor Nusis over.”

I tried to think through this, my mind spinning. “What makes you so sure the twitch themselves didn’t leave that key as a fake?”

“Because they went to the trouble of cleaning both the exterior and interior of the safe after they killed Nusis. The twitch is methodical, and careful—they don’t normally make mistakes that require cleaning. So…why would someone so careful manipulate and clean a safe after they’ve already robbed it? Why create this mess for themselves? The easiest answer is that they did not get what they sought and wished to hide that they’d ever sought it at all.”

“But…why would the Hazas risk so much over a reagents key, ma’am? And why would someone bother stealing it first?”

“Well, that assumes that the key you originally found actually was a reagents key,” she said. “And I’m now convinced that it wasn’t! I think it was something else entirely…Nusis herself was even puzzled by it. We asked her to identify what kind of key it was, and none of her tests could tell her—because it wasn’t a key at all, you see.”

“Then what was it?”

“The missing third you overheard Fayazi Haza discussing!” said Ana. “Something terribly important. The heart of all the sin that hangs over this canton, and perhaps the whole of the Empire. Now—get me to Vashta, quickly. For I know what we must do.”

“And what’s that?”

“Tell her that someone is going to try to kill Fayazi Haza,” said Ana simply.

---

—

“A…A THREAT AGAINST Fayazi Haza’s life?” said Vashta, horrified. “Again? Truly?”

“I’m afraid it is, ma’am,” said Ana. “There is a third assassin, and they struck again tonight. I am convinced that they mean her ill.”

Vashta paced the Iudex tower atrium, her face stricken, her black Legion’s uniform tinkling softly as all her heralds clinked against one another. “And…and this is who killed poor Nusis?”

“I am still unsure of that, ma’am,” said Ana. “But I think I can identify them. To do so, I will need to confer with Madam Haza, along with her engraver—for he has likely engraved many memories that may be useful to us in our search. Can we summon them here, to the Iudex tower, first thing tomorrow? The faster we move, the likelier we can ensure her safety.”

“I…I can, certainly,” said Vashta. “But, Dolabra, this is ill-timed…The leviathan approaches. The canton will likely devolve to chaos as it nears.”

“And that would be the best time for an assassin to strike. We must resolve this quickly. And, if she does agree to come, I would recommend giving Madam Haza the utmost protection. Any Legionnaire you can spare must be present, ma’am, along with Captain Miljin.”

“Of course. Yet is there no more you can tell me? I mean, who is this killer? And what is the nature of this threat against Fayazi Haza?”

“I cannot offer you anything of great certainty, ma’am. But I believe her engraver’s testimony can illuminate that. Now, with your leave, ma’am, Din and I must prepare for our interview tomorrow.”

She nodded. “Certainly. Certainly…”

I led Ana up the stairs, the whole of the tower creaking about us in the night wind.

“Just wish to comment, ma’am,” I said, “that, ah, I’ve no idea at all what’s going on anymore.”

“We build a trap, Din,” said Ana. “Vashta herself said that the only thing that would make Fayazi jump now would be if we said there was another threat to her life.” She grinned. “And that is what I just told her.”

“You lied to her, ma’am?”

“Oh, I did,” said Ana. “But not about that. There is a threat to Fayazi’s life—yet not the sort anyone expects.”

“Then…what did you lie to her about?”

“Well, for starters, I know who the third poisoner is, Din. And I now know how those ten Engineers died. And I also know what that reagents key truly was—and where it is now. I do feel a bit bad for lying to Vashta about all that, but…well, there is so much corruption in this canton that I worry an errant word from her could ruin my plot.”

We came to her door. I opened my mouth to say more, but she raised a finger.

“No time to explain, Din,” she said. “I must prepare my rooms for tomorrow, for I worry that all this could very well go awry. But listen, boy…” She gripped my arm tight. “I am going through this door, and after that, you are to never open it again, understood? Not without my saying it’s safe. Is that clear?”

“I…I don’t understand, ma’am,” I said, now thoroughly bewildered. “Why?”

“Do you understand that you shouldn’t open this door unless I tell you, child?” she hissed. “Yes? Then do as I say! I’d tell you why, but I’m sure you’d just try and stop me, and that would imperil many lives.”

“I’m your engraver,” I said indignantly. “Shouldn’t I be told of your schemes?”

“You’re right—you are my engraver. You are here to look, and see. So be down in the atrium first thing tomorrow, and be ready to look and see! And bring your sword. For if my conjectures prove true, we shall unmask a murderer—and a great deal more than that. Or we shall get all our throats slit.” She grinned again. “Now sleep, boy—if you can.” Then she shut the door.