‘... the Woodpecker ,' said Moist, more slowly.

‘You've got it. But we can't get it on to the Trunk. They're on to us'

‘Supposing I could get it on to the Trunk?' said Moist, staring at the lights. The towers themselves were quite invisible now.

‘You? What do you know about clacks codes?' said Undecided Adrian.

‘I treasure my ignorance,' said Moist. ‘But I know about people. You think about being cunning with codes. I just think about what people see—'

They listened. They argued. They resorted to mathematics, while words sailed through the night above them.

And Sane Alex said: ‘All right, all right. Technically it could work, but the Trunk people would have to be stupid to let it happen.'

‘But they'll be thinking about codes,' said Moist. ‘And I'm good at making people stupid. It's my job.'

‘I thought your job was postmaster,' said Undecided Adrian.

‘Oh, yes. Then it's my vocation.'

The Smoking Gnu looked at one another.

‘It's a totally mad idea,' said Mad Al, grinning.

‘I'm glad you like it,' said Moist.

There are times when you just have to miss a night's sleep. But Ankh-Morpork never slept; the city never did more than doze, and would wake up around 3 a.m. for a glass of water.

You could buy anything in the middle of the night. Timber? No problem. Moist wondered whether there were vampire carpenters, quietly making vampire chairs. Canvas? There was bound to be someone in the city who'd wake up in the wee small hours for a wee and think, ‘What I could really do with right now is one thousand square yards of medium grade canvas!' and, down by the docks, there were chandlers open to deal with the rush.

There was a steady drizzle when they left for the tower. Moist drove the cart, with the others sitting on the load behind him and bickering over trigonometry. Moist tried not to listen; he got lost when maths started to get silly.

Killing the Grand Trunk... Oh, the towers would be left standing, but it would take months to repair them all. It'd bring the company down. No one would get hurt, the Gnu said. They meant the men in the towers.

The Trunk had become a monster, eating people. Bringing it down was a beguiling idea. The Gnu were full of ideas for what could replace it - faster, cheaper, easier, streamlined, using imps specially bred for the job...

But something irked Moist. Gilt had been right, damn him. If you wanted to get a message five hundred miles very, very fast, the Trunk was the way to do it. If you wanted to wrap it in a ribbon, you needed the Post Office.

He liked the Gnu. They thought in a refreshingly different way; whatever curse hung around the stones of the old tower surely couldn't affect minds like theirs, because they were inoculated against madness by being a little bit crazy all the time. The clacks signallers, all along the Trunk, were... a different kind of people. They didn't just do their job, they lived it.

But Moist kept thinking of all the bad things that could happen without the semaphore. Oh, they used to happen before the semaphore, of course, but that wasn't the same thing at all.

He left them sawing and hammering in the stone tower, and headed back to the city, deep in thought.