Jon took point, Daphne behind him. They held their wands high, following a crooked footpath through the rock.
The Patronus moved ahead as their guide. Astoria and Harry fell in line behind the first two.
As they walked, Jon touched the walls with his wand, leaving neat marks on the stone. If they lost the way, they could retrace their steps.
The sound of water grew as they went. That, at least, was good news; running water meant the cave wasn't sealed. There was likely an exit somewhere.
They found the source soon enough. After squeezing through a narrow throat of passage, a stream appeared, spilling from a jut of rock. The water carried fine limestone sediment, and years of deposition had fused into a curtain of flowstone like a pale waterfall. On the streambed sat delicate, snowflake-clear crystals.
Jon halted. At minimum, they could wash their faces here and keep sharp.
The spring was icy and clean, drinkable without a second thought.
He set a fresh mark by the water, then they moved on behind the Patronus.
Minutes later, they stepped into a broad chamber, the walls shouldered up by strange columns where stalactites and stalagmites had grown together. From the ceiling hung stalactites like dangling human legs. The sight raised a crawl along the skin.
Astoria edged closer to Jon. Her foot slid on moss and she gave a small, involuntary cry.
In lifting her wandlight, she had seen them: bats. Hundreds upon hundreds crowded the cavern roof.
The beam struck the ceiling and the colony exploded. Thousands of bats dropped, screaming, battering toward the glow of Jon's and Daphne's wands.
Daphne's own scream tore loose.
The girls' voices only drew more. The swarm heaved toward them.
Jon seized Daphne's wrist and wrenched her wand out of her hand. In a panic she might fire off something like the Reductor Curse. A cave-in here would end all four of them.
Beside him, the other three had already crouched, arms over their heads, as the black hail fell.
"Incendio!"
Jon lifted the Elder Wand and spoke, calm and clear.
Heat bloomed. A ring of golden-red fire sprang up around the rock, bright as a brand. The nearest bats brushed it and flashed into flame. A harsh, meaty stink hit the air.
Fire danced in Jon Hart's eyes. He held the wand aloft like a torch, and fresh gouts surged from its tip. The ring braided with the new jets until the blaze became great, warming chains of flame.
They raked the cavern. The bats broke and fled, wheeling in panic, seeking any gap away from the burning magic hemming them in.
Within a minute, the cave was quiet again. The thick colonies along the ceiling were scorched away or driven deeper into the tunnels.
Jon exhaled and leaned against the wall, catching his breath. Even with the Elder Wand, it had cost him.
"Most beasts, magical or not, have fire-fear carved into them," he said softly, returning Daphne's wand.
She took it back without a word.
"It's over," Jon told Astoria, helping her to her feet. "Let's keep moving."
After the bats, they spoke less. The Patronus led; the four shadows followed.
Silence pressed in so deep they could hear one another breathe. The cave felt like it held out a cold hand, closing on their souls.
They dropped into another corridor and stretched back into single file.
They had bled more than two hours to this miserable warren.
At first, whenever a side opening appeared, someone would lean in for a look. Later, they only trailed the Patronus, moving by habit more than choice.
Astoria and Daphne were flagging. They'd likely never done a "trip" like this, never walked so far in one go.
Jon was about to call a rest when he spotted a pinprick of light ahead.
"Hold on a little longer," he said quickly. It looked like daylight.
Urged on, they picked their way toward it.
Just as he'd hoped, it was a way out—a tight mouth barely wide enough for one.
Jon eased his head and shoulders through. Dawn's sun was shouldering up at the world's edge. Fresh air snapped his mind clear. A wide river rolled past before them.
"We're finally out," he said, giving the Patronus a thumbs-up before dismissing it.
Without that guide, there was no chance they would have threaded this maze so quickly.
Across the rush of the river stood a sparse copse.
"We'll Apparate to the far bank," Jon called. "Harry, with me. Astoria, with your sister."
Apparition only reached as far as you could see or someplace well known to you. In the cave, they'd had no bearings, only black walls, and Apparition had been useless. Out here, with the exit found, the calculus changed.
Two white flashes later, all four stood on the opposite bank.
"What do we do now, Jon?" Harry lay back on a heap of what looked like twigs and leaves, gulping air to steady himself.