The limestone question was still turning over in his mind when a new sound reached them.
It came from the northeast. A steady percussion, low and heavy. Each impact followed the last at the same rhythm, regular enough that it was obvious after three strikes. Beorn listened and compared it to the sounds he knew.
Beorn stopped.
Around them the street reacted immediately.
A woman selling flatbread from a board balanced across two barrels turned her head toward the northeast. She slid the board back against the wall behind her, securing her goods without looking at anyone else.
A man guiding a loaded cart pulled the reins tight and halted his animal. He studied the same direction for a moment, then made a decision. He steered the cart into a narrow gap between two buildings and left it there.
At the edge of the street, two children leaned out of a doorway to look. An arm reached from inside and pulled them back without a word. The door closed.
The reaction had the efficiency of repeating behavior. These people had heard this sound before, and each of them already knew what to do.
"Northeast wall," Godric said.
Beorn had already started moving.
The street leading toward the miners' quarter was wide enough for the formation to keep pace. Beorn remembered this section from his walk before.
Low rows of patched buildings lined the street. Workers had stood outside them with tools that were kept maintained even though the mines themselves were silent. The habits of the trade had survived the loss of the work.
At the quarter's outer edge stood the section of wall he had marked earlier as the worst in the city. Timber braces supported the upper courses where the stone had failed.
The mortar between the joints looked dry and pale, thin lines of old work that had first been done poorly and later patched with even less care.
The sound grew stronger as they moved toward it. Close enough now that each impact carried through the ground before it reached the ear. Beorn felt the faint vibration through the soles of his boots a moment before the next strike landed.
The wall came into full view at the end of the road.
Two of Coss's men were already descending the steps from the parapet as Beorn's group arrived, moving quickly to positions at street level. A third stood at the top of the steps directing others.
The men spread outward to cover angles along the base of the wall, crossbows raised and ready. Their movement was quick but efficient. This was a routine they had executed before.
Four crown garrison soldiers stood near the bottom of the steps. Their spears rested across their bodies at loose angles, neither raised nor lowered.
One of them looked at Beorn, then at Godric, then at the men taking control of the stairs. He leaned toward the soldier beside him and said something too quiet to carry across the street.
Two of them drifted away from the steps in a direction that clearly had no objective. The other two followed. All four remained well back from the wall.
One of Coss's men stepped in front of Beorn at the bottom of the stairs and lifted a hand.
"The wall's already covered, my lord. We've got the defense handled."
Beorn raised the signet ring where the man could see it and continued forward.
The man hesitated with his hand still raised. Then he lowered it and stepped aside.
From the top of the wall the situation became clear.
Below the parapet, pressed against the northeastern face, were close to twenty monsters. The number shifted slightly as animals moved at the edges of the group, but the mass remained concentrated at the base of the wall. A fragment of memory came. Those were Greybacks.
They were larger than the name suggested. The basic body of a boar still showed underneath, but the environment had changed the species over generations.
The bodies were built forward, heavy through the shoulders. The head sat low, the hindquarters providing most of the drive when the animal pushed ahead.
Along the spine and across the shoulders, natural hide had been replaced by plates of mineralized tissue. The plates were dull grey-white and overlapped each other, forming a ridge beginning behind the skull and running halfway down the spine.
Midday light struck those plates and reflected almost nothing.
Between the largest sections the original hide remained visible, dark patches where the mineral growth had not yet sealed the gaps.
Each animal pressed forward using the reinforced front of its skull and shoulders against the weakest section of the wall.
The impacts were dull and steady. The stone at the base already showed the look of material that had endured this treatment many times before.
Movement caught the edge of Beorn's vision.
He glanced sideways. Aestrith stood beside the parapet with both hands flat against the stone. Her eyes were fixed on the animals below.
Beorn noted the posture, then turned his attention back to the wall.
Coss's men fired the first volley in two passes. The first row aimed at the leading animals to draw their attention. The second row fired into the cluster while those front animals were already reacting.
Crossbow bolts struck the mineral plates with a sharp crack followed by a duller note where the angle forced the bolt to deflect. Several bolts skidded away across the plate surfaces.
A second volley followed. Then a third, then more. The monsters recoiled from the front line, their movements uneven, the forward drive finally disrupted.
The disruption spread quickly through the rest of the group. Some animals turned left, others right.
The mass dissolved as instinct changed from pressure to retreat. The pack withdrew roughly a hundred yards from the wall before stopping.
At the top of the steps, Coss's officer gave a short order to the dozen or so men remaining on the parapet. They kept their crossbows aimed.
Beorn began walking the length of the wall section slowly. One hand rested on the parapet edge as he leaned out to examine the stone below.
The vertical crack he had noticed earlier extended farther than he had first estimated. From this angle he could follow it all the way down to the base course, where it widened into a pale gap where the stones had recently separated.
Along the lowest courses the mortar had degraded into powder in several places. The binding material had failed entirely, leaving loose aggregate sitting in the joints with nothing to hold it.
He continued to the next section. The mortar there was stronger, still aged but intact. The stones sat square against one another.
Then he reached the point where the wall curved slightly to follow the terrain.
At that bend the construction changed. The stone was older, cut differently. A different mason's method from another generation.
The seam between the two building phases ran directly through the bend, and it was the weakest line in the entire stretch. Years of heat expansion, cooling, and water infiltration had slowly shifted the materials in different directions.
Beorn stopped at that point.
Then he reached into his coat and removed the ledger.
The quarry route sketch he had drawn earlier occupied the right margin of the page, the line extending north toward the limestone deposits. The question mark marking the source point still waited unresolved.
He rotated the book and began adding new marks beside it.
He translated what he had just observed into a diagram. The crack. The failed mortar. The seam between construction phases. The points where the Greybacks had concentrated their pressure.
The sketch filled the margin faster than normal, each inch of page carried more marks than his normal notes during negotiations or planning sessions.
His hand placed every line with care, maintaining accurate proportions even at the small scale.
"How often," he said, still looking at the page.
Godric stepped beside him. "Attacks like this on this face? About thirty times in the last year. Ten the year before that."
Beorn kept writing.
Godric continued. "There used to be whole seasons where nothing reached the walls. The last couple of years haven't worked that way. It started increasing about a decade ago and never slowed down."
"What changed."
Godric studied the barren ground beyond the wall where the Greybacks lay scattered. "No one knows. Something changed in the wilderness."
The timing might matter. It might not. There was not enough information yet to determine whether the two facts connected.
Beorn wrote a number in the margin. Thirty attacks in the last year. Ten the year before. He drew a short line beneath them and left space to continue the record later.
"There's another section that's worse," Godric said.
Beorn looked up.
Godric pointed farther along the northeastern face beyond the bend where they stood.
At the far end of the visible wall the stone showed a different pattern of discoloration near the base. A dark vertical stain climbed the face, the mark left by water seeping through the interior long enough to reach the outside surface.
Beorn studied it.
Then he closed the ledger without finishing the final line.