They set off along Footpad Passage toward the bright lights of Wizard Way and Beetle began to explain. “At first I thought it was a drawing of a spider’s web, but then Romilly pointed out that it fit the shape of the Castle. So Ephaniah floated it in the Enhancing Tray to see if he could get anything else to show up. And it did. A very faint map of the Castle appeared and then we saw the title.”

“Which was?” asked Marcia.

“Vents: Cauldron cooling system.”

“Cauldron cooling—is this some kind of witch thing?”

“I don’t think it is. It is far too technical to be a witch thing and besides, they don’t really write stuff down, do they?”

“True,” said Marcia.

“Romilly pointed out that there were lots of breaks in the web and they all ended in a dot—as if someone had rested the pen on the paper for just a little too long. And we noticed that all the dots were in quiet alleyways. It was intriguing. So Romilly and I went out hunting, to see if there was anything visible aboveground.”

“And was there?” asked Marcia.

Beetle sighed. “No. It was the day after the Big Freeze came in and the snow had covered everything. At the time I thought that was really bad luck and that we’d have to wait until the thaw. But then last week Foxy came into work soaking wet and said he’d fallen into a puddle. Well, we all laughed—how could he possibly have fallen into a puddle with everything frozen solid? But Foxy got really annoyed and insisted on taking me to see the puddle.”

“I’d have thought a Chief Hermetic Scribe had better things to do than go and see a puddle, Beetle,” Marcia teased.

“Yeah. Well, it was either go and see the puddle or no more sausage sandwiches. Not from Foxy. Ever.”

“Ah. I see.”

“To my amazement there was a puddle. So sausage sandwiches were on me that day. The next day I heard about another one from Partridge and then another and another. It felt like all the scribes were at it, finding puddles. I got Partridge to draw a map of where they were and I had a weird idea. I superimposed it on the Vent web. And every puddle matched the dot at the end of a line. Every single one.”

“Well, well, well,” said Marcia.

They had reached Bott’s Cloaks, which proudly proclaimed above the door: WIZARD CLOAKS: OLD AND NEW, GREEN AND BLUE. PERFECT, PRELOVED CLOAKS ARE OUR SPECIALITY. Bott’s Cloaks was a large and normally rather exuberant shop opposite the Manuscriptorium, but now it was sadly subdued because its proprietor, Bertie Bott, was missing, presumed eaten. Mrs. Bott had draped the usual garish statues in black cloth, and a solitary candle burned in the window.

“Poor Bertie.” Marcia sighed and gazed at the window. “I feel responsible. If I hadn’t insisted on him being on guard . . .”

“But someone had to be on guard,” said Beetle. “If it hadn’t been Bertie it would have been another Wizard. And it wasn’t you that killed him. It was—well, actually, it was Merrin.”

“No,” said Marcia. “It was the Darke. Merrin was its tool, just as Simon was. The Darke finds people’s weaknesses and exploits them.”

“I guess so,” said Beetle. The talk of the Darke had made Beetle a little spooked and the thought of the empty Manuscriptorium was not inviting. Even though it was late, he said, “Ephaniah is doing a final Enhance on the Vent diagram tonight. He thought he saw the shadow of some handwriting and he’s going to have a closer look. I know it’s late, but would you like to come and take a look?”

“Most definitely,” Marcia said without hesitation. The thought of the ghost of Jillie Djinn staring at her empty-eyed when she came home was no more inviting for Marcia than the Manuscriptorium was for Beetle.

Down in the quiet, still whiteness of the Conservation basement, a bulky shape swathed in white robes was holding a transparent tray up to the light. Ephaniah Grebe, half man, half rat, turned to Marcia and Beetle. The lower half of Ephaniah’s face was, like his body, swathed in white. The shape beneath the silk wraps betrayed its ratness but his human brown eyes sparkled behind his spectacles as he gave a thumbs-up sign. Ephaniah put the tray down on the workbench and pushed a small white card across to Beetle and Marcia. It said: MILK, NO SUGAR, PLEASE.

“Huh?” said Beetle, puzzled.

Ephaniah made a sound that could have been a rat-laugh. He turned the card over. It now said: THE ENHANCEMENT IS COMPLETE.

Beetle and Marcia peered at the now thick and shiny piece of white paper lying in front of them. Ephaniah’s long, narrow ratlike finger traced some faint handwriting that was scrawled across the foot of the drawing like an afterthought. Marcia drew out her Enhancing Glass and offered it to Beetle.