The cold section of the Underways ran below the old drainage infrastructure from the Hollow's second construction phase — a period when the engineers had rerouted subsurface water flows to manage flooding in the lower districts, and had left behind a network of channels that no longer carried water but still carried cold, the way empty spaces held the temperature of what had last been in them.

The passage was wide enough for two people side by side, which meant that when they were moving in single file — Alden first, lamp forward — the space beside her felt like a presence rather than an absence. She had been in the Underways often enough now that the darkness had lost its initial quality of threat and become something closer to neutral, like the bad lighting in the lower Ash Annex corridors. You accommodated it. Your eyes found what light there was.

Alden stopped.

He stopped in the middle of the passage, not at a junction or a hazard, not because of a sound ahead. He stood still for a moment with his right hand moving to his left shoulder — not grabbing it, not pressing, just the flat contact of a hand resting against a surface, the way you rested a hand against something to check its temperature.

Then he continued walking.

She matched his pace and said nothing for another twenty meters. Then:

“Your left shoulder.”

He kept walking. “Sorry?”

“You've done that before. In cold sections especially. You put your hand on your left shoulder.” She kept her voice level. “The scar.”

A pause in his stride — not a full stop, just a fractional slowing that she caught because she had been watching. “Burn scars are sensitive to temperature changes. You know this.”

“I know burn scars are sensitive to temperature changes,” she said. “I also know that the naming bell in the High Ring shrine two weeks ago produced a secondary harmonic and your hand went to your shoulder before you were aware you were doing it. That's not a temperature response.”

He was quiet for a long moment. They were moving through the coldest section of the passage, the air cold enough to crystallize the edges of her exhaled breath in the lamp light.

“I've had the scar since I was young,” he said. “I've always been told it was a burn from a heating accident when I was an infant. I have no reason to believe otherwise.”

“Do you believe it?”

Another pause. “I don't know what I believe about it,” he said. “I know what I was told. I know the scar has always done things I can't explain and that I've spent most of my life explaining in other ways.” He glanced at her over his shoulder — brief, in the dark, only half his face visible in the lamp light. “Is that honest enough?”

“It's more honest than most answers I get,” she said.

They came to a section where the passage floor dropped six inches without warning — a structural drop from a repair that had raised the level of the surrounding floor without leveling the old section. Alden stepped down easily. He turned and offered his hand.

She took it. He held her wrist as she stepped down, steadied her on the landing, and let go. The contact lasted approximately two seconds.

She was aware of it in the way she was aware of the cold and the lamp light — as a physical fact of the space they were moving through.

The passage opened into a wider section — a junction point, a small landing with a ceiling high enough to stand fully upright. Alden set the lamp down on a stone projection and they took a brief rest stop, the way they always did at junction points, checking bearings and eating quickly if either of them had food.

She had a piece of hard bread from her coat pocket. He had nothing. She broke the bread and gave him half.

He took it without commenting on this, which was the appropriate response.

After a moment, she said: “Do you trust me?”

He looked at her. The lamp was on the stone projection between them, and in the low light his face was partly in shadow, which made his expression harder to read than usual and also meant she was reading it more carefully than usual.

“Yes,” he said. Simply.

“Then listen to what I'm going to tell you.” She took a breath. “I've found a record from six years ago. A Vaultbinder examination record for a body that had died from a failed Graftmark. The notation on the record says the Graftmark failed because the name it was anchored to was spoken aloud by someone outside the ritual system. The person carrying the Graftmark didn't survive.” She watched his face. “A functioning Graftmark is anchored to a name. The name of a dead person, used to create the binding.”

He was still.

“Cassian's mark moves under his skin,” she said. “The second body had a failed Graftmark on its left shoulder. The first body had a Vaultmark that was cut away, with THE SKY LIES carved beneath it.” She paused. “Your scar is on your left shoulder. The same location as the failed mark on the second body.”

The quality of his stillness changed.

“I'm not saying I know what's under your scar,” she said. “I'm saying I've been putting things together for three weeks, and that particular parallel is one I can't account for any other way.”

Alden looked at the wall across from them. Not at her. At the stone wall of the tunnel, the way he sometimes looked at things when he needed to process without the additional input of someone's face.

“Do you trust me?” he said.

She had asked him that. He was returning it.

“I trust that you're telling me what you know,” she said. “I'm not certain you know everything there is to know about yourself.”

“That's fair,” he said.

He picked up the lamp. He stood up. He looked at her with the expression she had learned to read as the one he wore when he had decided something but had not yet decided to say it.

“When this is over,” he said. “When we know what we need to know. I'll look at what's under it.”

“With Mother Sable?” she said. Because she had put that piece together too — the Ash Saint in the lower Rings who knew how to hide marks, who was the only person in this part of the city with the knowledge to have made a burn scar that wasn't a burn scar.

He looked at her steadily. “With Mother Sable,” he said.

They continued through the tunnel.