F eed the Magogs, do not touch Sleuth, and don't go nosing around my room. Got that?" Simon Heap told his scowling assistant, Merrin Meredith.

"Yeah, yeah," sulked Merrin, who was sitting listlessly on the one comfortable chair in the Observatory. His dark, straggly hair hung limply over his face, masking a large pimple in the middle of his forehead that had sprung up overnight.

"You got that?" asked Simon crossly.

"I said 'yeah,' didn't I?" mumbled Merrin, swinging his long, gangly legs so that his feet hit the chair with an irritating regularity.

"And you better keep the place tidy," Lucy Gringe told him. "I don't want to come back to a complete mess."

Merrin jumped up and made a mock bow to Lucy. "Yes, Your Ladyship. Can I do anything else for you, Your Ladyship?"

Lucy Gringe giggled.

Simon Heap frowned. "Come on, Lucy," he said irritably. "If you want to get to the Port before nightfall, that is."

"Wait a minute, I've just got to find my - "

"I've got your bag and your cloak. Come on, Luce." Simon strode across the Observatory, his footsteps sounding hollow on the black slate, and disappeared through the granite arch that led to the stairs. "And, Merrin - don't do anything stupid." Simon's voice echoed up the stairs.

Merrin kicked the chair angrily and a cloud of dust and disturbed moths flew out. He was not stupid.

He was not, not, not stupid. Merrin had spent the first ten years of his life being called stupid by his old master, DomDaniel, and he had had enough of it. Merrin had been mistakenly known as Septimus Heap for all those years, but however hard he had tried, he had been a poor substitute for the real Septimus. DomDaniel never did realize the mistake - or the reason why his hapless Apprentice never managed to do anything right.

Scowling, Merrin threw himself back into the old armchair. He watched Lucy Gringe, plaits and ribbons flying, rush around, gathering up her last-minute bits and pieces.

At last Lucy was ready. She snatched up the multicolored scarf that she had knitted for Simon during the long winter evenings in the Harbor and Dock Pie Shop and ran after him. As she, too, disappeared under the gloomy granite archway, she gave Merrin a little wave. Merrin lost his scowl and waved back. Lucy always managed to make him smile.

Happy to be away from what she considered to be the creepiest place on earth, Lucy did not give Merrin another thought as he listened to the hollow sound of her boots beginning the long descent to the cold, damp, Wurm-slimed burrow where Simon's horse, Thunder, was stabled.

As the sound of Lucy's boots faded away into the distance and a heavy silence replaced it, Merrin sprang into action. He seized a long pole and quickly began lowering the black blinds that covered the skylight at the top of the room - it poked up from the rough grass and rocky outcrops at the top of the tall slate cliffs, the only part of the Observatory visible aboveground. As Merrin pulled down blind after blind, the huge room slowly darkened until a dim twilight reigned.

Merrin went over to the Camera Obscura - a large, concave dish that filled the center of the circular room - and gazed at it with a rapt expression. What had been a blank white dish in the early-morning sun streaming through the skylight was now transformed to show a beautifully detailed, colorful scene. Entranced, he watched a line of sheep silently amble along the cliff top above the ravine, the pink clouds of the sunrise drifting slowly behind them.

Merrin reached up, took hold of a long pole hanging down from the center of the skylight, and began to turn it. A protesting squeak started up from a small bonnet at the apex of the skylight, which held the lens that focused the scene onto the dish below. As Merrin slowly turned the bonnet through a full circle, the picture before him changed, showing a silent panorama of the outside world. Merrin took a turn through the whole 360 degrees just for fun and then sought out the spot he wished to watch. He let go of the pole, the squeaking stopped and, pushing his straggly black hair out of his eyes, Merrin leaned forward and stared intently at the scene before him.

The dish showed a long, winding path that snaked down between rocky outcrops. A deep ravine could be seen to its right, and sheer slate cliffs to the left, broken only by an occasional rock fall or cascade of gravel. Patiently Merrin waited until at last he saw Thunder come into view. The horse slowly picked his way along the path, carefully guided by Simon, his black cloak wrapped around him against the early-morning chill. He was muffled in Lucy's scarf, the end of which she had also wound around her own neck. Lucy sat behind Simon, swathed in her precious blue cloak, her arms clasped tightly around his waist.

Merrin grinned as he watched the horse travel silently across the dish. He was, he said to himself, seeing them off the premises. As he watched Thunder's slow progress, Merrin congratulated himself on having engineered the whole thing. From the moment Lucy Gringe had arrived a couple of weeks ago - accompanied by an immensely irritating rat that Merrin had also seen off the premises with a well-aimed kick - Merrin had started planning. His opportunity arose sooner than he had expected.

Lucy wanted a ring - and not any old ring either. A diamond ring.

Merrin had been surprised at how quickly Simon had agreed to Lucy's way of thinking about many things - even diamond rings. Seizing his chance, Merrin had suggested that he could look after the Observatory while Simon took Lucy to the Port to find a ring. Simon said yes, as he had in mind a visit to Drago Mills's warehouse clearance sale, which the rat had talked about at length. It had started the week previously due to the death of the owner of the warehouse, and was apparently full of the most amazing bargains. Lucy Gringe, however, had other ideas. She had already decided on the perfect ring and it was definitely not from Drago Mills's warehouse clearance sale.

At last Merrin's patience was rewarded by the sight of Thunder carrying his two riders off the edge of the dish. As the horse's tail disappeared Merrin let out a loud whoop. At last, at long last - after spending his whole life being told what to do by someone else - he was free!