“Okeydokey. No worries. Right away.”

Rupert Gringe shook his head as he watched the ExtraOrdinary Wizard, the Castle Alchemist and their disputed Apprentice squash uncomfortably into a bright pink paddleboat and head unsteadily along the Moat, while the ExtraOrdinary Wizard smashed at the ice with a pointed stick. He was glad it wasn’t him wedged between those two fusspots, doing all the paddling. He wished his new brother-in-law a silent good luck and went back in to his warm boathouse.

The UnderFlow was dark and cold, but it was ice free. The paddleboat only just fit the narrow tunnel and the sound of the paddles turning was magnified a hundred times by the brick walls. Marcia sat in the prow like a large purple dog. She leaned forward, pointing her FlashLight so that it illuminated the low-arched tunnel that ran before them. The sound of the paddles rebounded off the walls, filling their heads with noise. Septimus paddled fast, churning up the murky water and sending it splashing up against the slimy brick and dripping into the boat. It was the first time he had been underground since his time in the Darke Halls, and he was surprised how scared he felt.

Ten long minutes after Septimus had steered the paddleboat into the UnderFlow, the tunnel widened out and he sensed the faint, acrid smell of smoke. He slowed his paddling and took the boat into a wide, low-roofed cavern—they had reached the UnderFlow Pool. Relieved, Septimus let go of the paddles and sat up straight to get his breath back.

Septimus knew exactly where they were—he had last seen this place five hundred years ago. But then it had had a beautiful lapis-lazuli-domed roof; now all was dismal and dark. He took hold of the paddle handles again and maneuvered the little boat alongside the Quay. Marcellus leaned out and tied it up.

No one spoke. Marcellus felt too emotional. Marcia had been overcome with a sense of mystery—she was entering a part of the Castle about which she knew nothing. That, for an ExtraOrdinary Wizard, was strange in itself. But what was even odder was the sense that this had once seen something so terrible that it had very nearly destroyed the Castle. And now here they were, three people in a ridiculous little pink paddleboat, the first to come back to the scene for nearly five hundred years.

Septimus jumped out of the boat. The Quay was slimy underfoot and he skidded and slipped. He broke his fall with his hands and when he stood up he saw in the light of the FlashLight that his palms were black.

“Soot,” said Marcellus grimly.

Suddenly, Septimus realized why everything was black. He looked around, seeing the cavern with new eyes. “Everywhere,” he whispered.

“Yes,” said Marcellus heavily. He had forgotten just how bad it was—there had been no Drummins here to clean up. He took out a tinderbox and a sheet of metal gauze, which he folded to make a pyramid shape. From his pocket he produced a small fat candle, which he lit and placed in a candleholder, then put the pyramid of metal gauze over it.

“What are you doing?” asked Marcia.

“Preventing any explosions.”

“Explosions?” Marcia’s voice took on a slight squeak.

“Gases. Flammable. Just in case,” explained Marcellus.

“We can use my FlashLight. That won’t explode.”

“Thank you, Marcia, but I want to do this my way. With my light only, if you don’t mind.”

Marcia heard the strain in Marcellus’s voice. She imagined how she would feel going back to the Wizard Tower after some terrible disaster had ruined it—a disaster that she had caused. It did not bear thinking about.

“Of course, Marcellus,” she said. “I don’t mind at all.” And she switched off her FlashLight.

There were three smoke-blackened arches on Alchemie Quay, two of which were bricked up. Marcellus headed for the open left-hand archway, where he stopped and turned, his face eerily illuminated by his candle—something that always gave Septimus the creeps.

“We will now enter the Labyrinth,” he said, his voice hushed. “Please be aware that it does not run to a standard pattern. There are branches off to other smaller labyrinths and tunnels. Be sure to follow me and keep close. If you lose sight of me, stay where you are and call out. I will come and find you.”

Septimus remembered the Labyrinth well, but then it had been a beautiful, sinuous snake of a tunnel—brilliant with smooth, blue lapis lazuli walls shot through with gold and rare streaks of red and lit by rushlights. Now, like everything else, it was black with soot. Even though Septimus could recall all the tunnels and turnings, it looked so different that he doubted he would be able to find his way now.

Together Marcia and Septimus followed Marcellus through the arch and kept close behind him, the sound of their footsteps dulled by the carpet of soot. Marcellus trod carefully, after his first footsteps had raised a cloud of soot into the air and set everyone coughing and spluttering. The three walked slowly through the black coils of the Labyrinth, as subdued as if they were following a body on its way to its Leaving Boat. Even so, the soot rose into the air and tickled its way into their lungs, making them taste the fire of so long ago.