While Septimus sat rereading his letter, the messenger who had delivered it was suffering from an attack of cold feet. Even the two pairs of thick, stripy socks that Lucy Gringe habitually wore in the winter were no help that cold morning as she hung back in the shadows of the North Gate gatehouse, trying to pluck up the courage to announce herself to her mother.

Lucy had arrived at the Gatehouse early. She wanted to speak to her father first, before her mother ventured outside with his early-morning cocoa. Despite her father's gruff exterior, Lucy knew that Gringe would be thrilled to see her. "Dad's an old softy, really," she had told Simon before she had left. "It's Mum who'll be difficult."

But Lucy's plan had gone awry. She had been thrown by the unexpected appearance of a makeshift lean-to shelter along the side of the gatehouse, beside the road leading to the bridge. A sign on the shelter announced it to be CAFe LA GRINGE, from which came the (unfortunately) unforgettable smell of her mother's stew. This was accompanied by the equally unmistakeable sound of her mother cooking - clanging saucepan lids, muttered curses, and ill-tempered thumps and thuds.

Lucy stood in the shadows wondering what to do. Eventually the rank smell of the stew drove her to a decision. She waited until her mother was looking into one of the deep stew pans and then, head held high, Lucy marched right past CAFe LA GRINGE. It worked. Mrs. Gringe, who was wondering if anyone would notice the mouse that had fallen in overnight and suffocated, did not look up.

Gringe, a heavyset man with close-shorn hair and wearing a greasy leather jerkin, was sitting in the gatehouse keeper's lodge. He was keeping out of the chilly wind that blew off the Moat and, more importantly, out of the way of the stew. It was a quiet day. Everyone in the Castle was either at the last day of the Traders' Market - which had stayed later than usual that year - or were busy getting ready for the festivities of the Longest Night, when candles would be lit in every window throughout the Castle. And so, apart from taking toll money from a few bleary Northern Traders first thing that morning, Gringe had had nothing better to do than polish the few coins he had collected - a job he had taken over from Mrs. Gringe, now that she was, as he frequently complained, obsessed with stew.

When Gringe looked up at the newcomer, who he assumed was about to add to his meager pile of coins, he did not at first recognize his daughter. The young woman with big brown eyes and a nervous smile looked far too grown-up to be his little Lucy who, in her absence, had become ever younger in Gringe's fond memory. Even when the young woman said, "Dad!" a little tearfully, Gringe stared at Lucy uncomprehending, until his cold, bored brain at last made the connection. And then he sprang to his feet, enveloped Lucy in a huge hug, lifted her off her feet and yelled, "Lucy! Lucy, Lucy!"

A wave of relief swept over Lucy - it was going to be all right.

An hour later, sitting in the room above the gatehouse with her parents (while the bridge boy looked after the bridge and the stew looked after itself), Lucy had revised this opinion: It was possibly going to be all right, if she was very careful and didn't upset her mother too much.

Mrs. Gringe was in full flood, recounting for the umpteenth time the long list of Lucy's transgressions. "Running off with that awful Heap boy, not a care about me or your father, gone these last two years with never a word . . ."

"I did write to you," Lucy protested. "But you never replied."

"You think I got time to write letters?" asked Mrs. Gringe, insulted.

"But Mum - "

"I got a gatehouse to run. Stew to cook. On me own." Mrs. Gringe looked pointedly at both Lucy and Gringe who, to his discomfort, now seemed to be included in Lucy's wrong-doings. He stepped in hastily.

"Come, come, dear. Lucy's all grown up now. She got better things to do than live with her old mum and dad - "

"Old?" said his wife indignantly.

"Well, I didn't mean - "

"No wonder I look old. All that worry. Ever since she was fourteen she's bin running after that Heap boy. Sneaking out with him, even trying to marry him, for goodness' sake, and getting us into terrible trouble with them Custodians. And after all that we take her back out of the goodness of our hearts and what does she do? She runs off again! And never a word. Not a word . . ." Mrs. Gringe got out a stew-stained handkerchief and began noisily blowing her nose into it.

Lucy hadn't expected it to be this bad. She glanced at her father.

Say sorry, he mouthed.

"Um . . . Mum," Lucy ventured.

"What?" came her muffled voice.

"I . . . I'm sorry."

Mrs. Gringe looked up. "Are you?" She seemed surprised.

"Yes. I am."

"Oh." Mrs. Gringe blew her nose loudly.

"Look, Mum, Dad. The thing is, me and Simon, we want to get married."

"I'd 'ave thought you'd already done that," her mother sniffed accusingly.

Lucy shook her head. "No. After I ran away to find Simon - and I did find him" - (Lucy refrained from adding "so there," as she would have done not so long ago) - "well, after I found him I realized that I wanted us to be married properly. I want a white wedding - "

"White wedding? Huh!" said Mrs. Gringe.

"Yes, Mum, that's what I want. And I want you and Dad to be there. And Simon's Mum and Dad too. And I want you to be happy about it."

"Happy!" Mrs. Gringe exclaimed bitterly.

"Mum . . . please, listen. I've come back to ask if you and Dad will come to our wedding."

Her mother sat for a while digesting this as Lucy and Gringe looked on anxiously. "You really are inviting us to your wedding?" she asked.

"Yes, Mum." Lucy pulled a crumpled card edged with white ribbon from her pocket and handed it to Mrs. Gringe, who squinted at it suspiciously. Suddenly she leaped to her feet and flung her arms around Lucy. "My baby," she cried. "You're getting married." She looked at Gringe. "I'll need a new hat," she said.

There was a sudden sound of thudding boots on the steps leading to the room and the bridge boy burst in. "Whatddyou charge an 'orse?" he demanded.

Gringe looked annoyed. "You know what to charge. I left you the list. Horse and rider: one silver penny. Now go an' get the money before they stop hangin' around waitin' for an idiot like you to ask stupid questions."

"But what if it's just an 'orse?" the bridge boy persisted.

"What, a runaway horse?"

The bridge boy nodded.

"Charge the horse whatever it's got in its wallet," said Gringe, raising his eyes to heaven. "Or you can hang on to the 'orse and charge the owner when 'e catches up with it. What do you think?"

"Dunno," said the bridge boy. "That's why I come and asked."

Gringe heaved a heavy sigh. "I better go an' sort this," he said, getting to his feet.

"I'll give you a hand, Dad," said Lucy, not wanting to be left alone with her mother.

Gringe smiled. "That's me girl," he said.

Gringe and Lucy found a large black horse tied up to a ring in the gatehouse wall. The horse looked at Lucy, and Lucy looked at the horse.

"Thunder!" Lucy gasped.

"Nah," said Gringe, looking up at the clouds. "Looks more like snow to me."

"No, Dad," said Lucy, stroking the horse's mane, "the horse - it's Thunder. Simon's horse."

"Ah. So that's how you got here."

"No, Dad. I didn't come on the horse. I took the Port barge."

"Well, that's good. I were a bit worried. He's got no saddle or anything. Not safe riding like that."

Lucy looked puzzled. She stroked Thunder's muzzle and the horse pushed his nose into her shoulder. "Hello, Thunder," she said. "What are you doing here?"

Thunder looked at her. There was an expression deep in the horse's eyes that Lucy wished she understood. Simon would know, she thought. He and Thunder always knew what each other were thinking. Simon and Thunder . . . suddenly Lucy knew. "Simon! Something's happened to Simon. Thunder's come to tell me!"

Gringe looked concerned. Not more trouble, he thought. Mrs. Gringe was right. Ever since Lucy had met the Heap boy something was always going wrong. He looked at his daughter's worried expression and, not for the first time, he wished she had met a nice, straightforward Castle boy all those years ago.

"Lucy, love," he said gently. "It might not even be Thunder. There're a lot of black horses about. And even if it is 'im, well, it don't mean anything bad. In fact, it's a stroke a luck. The horse got loose, it's come all the way through the Farmlands and no one's pinched it - which is a miracle - it's found its way into the Castle and now it's found you." Gringe wanted so much to make it all right for Lucy. He smiled encouragingly. "Look, love. We'll find 'im a saddle and all that kind of horse stuff and you can ride 'im back to the Port. Better than that smelly old barge any day."

Lucy smiled uncertainly. She wanted everything to be all right too.

Lucy led a reluctant Thunder around to the gatehouse stable. When she left, after giving him fresh hay and water and covering him with a warm horse blanket, Thunder tried to follow her out. Lucy quickly closed the bottom half of the stable door. Thunder stuck his great head out of the open top door and looked reproachfully at her.

"Oh, Thunder, tell me Simon's all right. Please," she whispered.

But Thunder was saying nothing.

A few minutes later Mrs. Gringe came down to check on the stew. She was just in time to see Lucy, ribbons flying, racing off into the warren of houses that backed up to the Castle walls. Convinced that Lucy was running away again, Mrs. Gringe stomped over to the nearest stew pot and poked angrily at it. She was, however, pleased to see that the mouse had incorporated nicely into the brown sludge.

Lucy was not running away. She was heading for the steps up to the path that ran along the top of the Castle walls and would take her to the East Gate Lookout Tower - the headquarters of the Message Rat Service, run by Stanley, his four ratlets (now fully grown) and their assorted friends and hangers-on.

As Lucy strode along the walls, she composed a variety of messages to Simon. By the time she breathlessly pushed open the little door of the East Gate Lookout Tower and stepped into the Message Rat Office, she had decided on something short and simple (and also cheap): Thunder here. Are you all right? Send return message. Lu xxxxxx

Half an hour later, Stanley had just caught the mid-morning Port barge. He was unsure whether to be flattered or annoyed that Lucy had insisted that she trusted no rat but him to take the message. After half an hour spent hiding out in a fish basket, trying to avoid the barge cat, Stanley decided he was most definitely annoyed. He was going all the way to the Port just to deliver a weather bulletin. Added to that, he had just realized who the recipient of the message was - Simon Heap was one of the Heap Wizarding family. And Stanley was of the same mind as Mrs. Gringe on this one: Heap Wizards were bad news.