They broke a rule by accident. At least it began by accident. The west residence heating stopped working during one particularly cold July morning. Mae sent everyone to breakfast wearing jumpers and said maintenance would fix it before lunch. By lunch, the room was still cold. By dinner, Harper had turned Bag Bed into a blanket fortress.

"We live here now."

Ava stood outside it.

"We already lived here."

"Different government."

Jasper crawled inside because it was warmer. Ava lasted four minutes before joining them. At eight o'clock, the heating pipes in the western wall made a loud bang. Then another. A small panel beside the wardrobe popped open. Everyone stared. Behind it was darkness. Harper emerged from the blanket fortress immediately.

"Absolutely not," Ava said.

"I haven't moved."

"Your face moved."

Jasper approached the panel. A cold draught came through. Not sea air. Dust and stone. He shone his bedside lamp inside. A narrow maintenance space ran behind the wall, just wide enough for pipes and a person to crouch.

"Heating access," Ava said.

Harper said, "Tunnel."

"It is a service cavity."

"Tunnel."

Jasper found a metal label on the inside edge. WEST RESIDENCE HEAT LOOP - ACCESS STAFF ONLY

"Staff only," he said.

Harper sighed.

"Everything interesting is staff only."

A pipe banged again. Warm air puffed from somewhere inside. Then the light at the end of the cavity flickered. Not Jasper's lamp. Farther down. A faint blue glow. The trio went quiet.

"Maintenance worker?" Jasper whispered.

Ava said, "Could be." Harper called, "Hello?" No answer. The glow moved. Jasper's chest tightened. Sea pressure. Here? Inside the wall? That made no sense. He crouched closer.

"I feel it."

Ava's expression changed.

"Then close the panel."

Harper looked surprised.

"Really?"

"Yes. Staff only plus unknown light plus Jasper's sea thing. That's three reasons."

Harper thought.

"Fair."

Jasper reached for the panel. The blue glow brightened. A sound came from inside. Metal scraping stone. Then something small rolled out of the darkness and stopped near Jasper's hand. A brass disc. Old. Green around the edges. Stamped with a wave symbol. Ava stared.

"Do not touch it."

Jasper was already not touching it. Harper said, "Why?"

"Because it came from a restricted tunnel by itself."

"Strong argument."

They called Mae. Mae called maintenance. Maintenance called Professor Crowe. Within twenty minutes Room Fourteen had four adults in it and no children allowed near the wardrobe. Professor Crowe wore gloves and lifted the brass disc into a small box.

"Where was it?"

Jasper explained.

"And you felt the marine sensation?"

"Yeah."

Crowe looked into the service passage.

"Interesting."

Harper said, "What is it?" Crowe held up the box.

"Old ward token."

Ava leaned forward.

"For what ward?"

"That is what I intend to find out."

"Deepwater?"

Crowe's eyebrows rose.

"You three have been reading."

Harper said, "The goat has more records." Crowe looked confused. Ava said, "Library history."

"Right."

The adults opened the service passage properly. The blue light came from a maintenance charm farther inside. Boring. The token had likely been knocked loose when pipes shifted. Also boring. Jasper's pressure remained unexplained. Not boring. They were sent to the common room while repairs continued. Harper dropped onto a sofa.

"We did everything right."

Ava nodded.

"We did."

"And still found a secret tunnel."

"Service cavity."

"Secret tunnel."

Jasper looked toward the closed residence door.

"Why did I feel it?"

Ava pulled out her notebook.

"Maybe the token."

"How?"

"Old marine ward. If it was designed after Deepwater—"

"We don't know it was."

"Correct."

Harper groaned.

"I hate when both of you become sensible at the same time."

The heating was repaired before bedtime. Professor Crowe returned the next morning. She did not return the brass disc.

"It predates Deepwater," she said. "Old harbour ward token. Probably part of a system retired decades ago."

Ava asked, "Why did Jasper feel the sea when it moved?" Crowe looked at him.

"I don't know."

Jasper nodded. The answer no longer surprised him. Crowe continued.

"But the token was designed to register large changes in water pressure near the cliffs. It may hold residual magic from repeated use."

Jasper thought about memory. Not only living things remembered. Magic could leave traces too. That made the world more complicated. It also gave him something useful. Not every strange feeling meant the presence was actively speaking to him. Sometimes old magic could echo. Ava added a new heading to her notebook: PRESENCE vs RESIDUE? Jasper approved. Harper drew a tiny tunnel beside it. Ava tried to erase it. Harper protected the drawing with both hands. Some mysteries were easier than others.