Mrs Palm cleared her throat. 'This has gone far enough. You are correct, Sir Samuel,' she said. 'We were all sent a note.' She handed a slip of paper to Vimes. It had been written in capitals. 'And I can see we have been misinformed,' she added, glaring at Boggis and Downey. 'Do allow me to apologize. Come, gentlemen.'

She swept out of the door. Boggis followed her quickly.

Downey dabbed at his nose. 'What's the guild price on your head, Sir Samuel?' he said.

'Twenty thousand dollars.'

'Really? I think we shall definitely have to upgrade you.'

'Delighted. I shall have to buy a new beartrap.'

'I'll, er, show you out,' said Carrot.

When he hurried back he found Vimes leaning out of the window and feeling the wall below it.

'Not a brick dislodged,' Vimes muttered. 'Not a tile loose... and the front office has been manned all day. Odd, that.'

He shrugged and walked back to his desk, where he picked up the note.

'And I shouldn't think we'll be able to find any Clues on this,' he said. 'There's too many greasy fingermarks all over it.' He put down the paper and glared at Carrot. 'When we find the man responsible,' he said, 'somewhere at the top of the charge sheet is going to be Forcing Commander Vimes to Tip a Whole Bottle of Single Malt on to the Carpet. That's a hanging offence.' He shuddered. There were some things a man should not have to do.

'It's disgusting!' said Carrot. 'Fancy them even thinking that you'd poison the Patrician!'

'I'm offended that they think I'd be daft enough to keep the poison in my desk drawer,' said Vimes, lighting a cigar.

'Right,' said Carrot. 'Did they think you were some kind of fool who'd keep evidence like that where anyone could find it?'

'Exactly,' said Vimes, leaning back. 'That's why I've got it in my pocket.'

He put his feet on the desk and blew out a cloud of smoke. He'd have to get rid of the carpet. He wasn't going to spend the rest of his life working in a room haunted by the smell of departed spirits.

Carrot's mouth was still open.

'Oh, good grief,' said Vimes. 'Look, it's quite simple, man. I was expected to go At last, alcohol! , and chugalug the lot without thinking. Then some respectable pillars of the community' - he removed the cigar from his mouth and spat -'were going to find me, in your presence, too -which was a nice touch - with the evidence of my crime neatly hidden but not so well hidden that they couldn't find it.' He shook his head sadly. 'The trouble is, you know, that once the taste's got you it never lets go.'

'But you've been very good, sir,' said Carrot. 'I've not seen you touch a drop for—'

'Oh, that,' said Vimes. 'I was talking about policing, not alcohol. There's lots of people will help you with the alcohol business, but there's no one out there arranging little meetings where you can stand up and say, My name is Sam and I'm a really suspicious bastard. '

He pulled a paper bag out of his pocket. 'We'll get Littlebottom to have a look at this,' he said. 'I damn sure wasn't going to try tasting it. So I nipped down to the canteen and filled a bag with sugar out of the bowl. It was but the work of a moment to fish Nobby's butts out of it, I might add.' He opened the door, poked his head out into the corridor and yelled, 'Littlebottom!' To Carrot he added, 'You know, I feel quite perked up. The old brain has begun to work at last. You know the golem that did the killing?'

'Yes, sir?'

'Ah, but do you know what was special about it?'

'Can't think, sir,' said Carrot, 'except that it was a new one. The golems made it themselves, I think. But of course they needed a priest for the words and they had to borrow Mr Hopkinson's oven. I expect the old men thought it would be interesting. They were historians, after all.'

It was Vimes's turn to stand there with his mouth open.

Finally he got control of himself. 'Yes, yes, of course,' he said, his voice barely shaking. 'Yes, I mean, that's obvious. Plain as the nose on your face. But... er, have you worked out what else is special about k?' he added, trying to keep any trace of hope out of his voice.

'You mean the fact it's gone mad, sir?'

'Well, I didn't think it was winner of the Ankh-Morpork Mr Sanity Award!' said Vimes.

'I mean they drove it mad, sir. The other golems. They didn't mean to, but it was built-in, sir. They wanted it to do so many things. It was like their... child, I think. All their hopes and dreams. Arid when they found out it'd been killing people... well, that's terrible to a golem. They mustn't kill, and it was their own day doing it—'

'It's not a great idea for people, either.'

'But they'd put all their future in it—'

'You wanted me, Commander?' said Cheery.

'Oh, yes. Is this arsenic?' said Vimes, handing her the packet.

Cheery sniffed at it. 'It could be arsenous acid, sir. I'll have to test it, of course.'

'I thought acids sloshed about in jars,' said Vimes. 'Er ... what's that on your hands?'

'Nail varnish, sir.'

'Nail varnish?'

'Yes, sir.'

'Er... fine, fine. Funny, I thought it would be green.'

'Wouldn't look good on the fingers, sir.'

'I meant the arsenic, Littlebottom.'

'Oh, you can get all sorts of colours of arsenic, sir. The sulphides - that's the ores, sir - can be red or brown or yellow or grey, sir. And then you cook them up with nitre and you get arsenous acid, sir. And a load of nasty smoke, really bad.'

'Dangerous stuff,' said Vimes.

'Not good at all, sir. But useful, sir,' said Cheery. 'Tanners, dyers, painters... It's not just poisoners that've got a use for arsenic.'

'I'm surprised people aren't dropping dead of it all the time,' said Vimes.

'Oh, most of them use golems, sir—'

The words stayed in the air even after Cheery stopped speaking.

Vimes caught Carrot's eye and started to whistle hoarsely under his breath. This is it, he thought. This is where we've filled ourselves up with so many questions that they're starting to overflow and become answers.

He felt more alive than he had for days. The recent excitement still tingled in his veins, kicking his brain into life. It was the sparkle you got with exhaustion, he knew. You were so bone-weary that a shot of adrenalin hit you like a falling troll. They must have it all now. All the bits. The edges, the corners, the whole picture. All there, just waiting to be pieced together...

'These golems,' said Carrot. 'They'd be covered in arsenic, would they?'

'Could be, sir. I saw one at the Alchemists' Guild building in Quirm and, hah, it'd even got arsenic plated on its hands, sir, on account of stirring crucibles with its fingers...'

'They don't feel heat/ said Vimes.

'Or pain,' said Carrot.

'That's right,' said Cheery. She looked uncertainly from one to the other.

'You can't poison them,' said Vimes.

'And they'll obey orders,' said Carrot. 'Without speaking.'

'Golems do all the really mucky jobs,' said Vimes.

'You could have mentioned this before, Cheery,' said Carrot.

'Well, you know, sir ... Golems are just there, sir. No one notices golems.'

'Grease under his fingernails,' said Vimes, to the room in general. 'The old man scratched at his murderer. Grease under his fingernails. With arsenic in it.'

He looked down at the notebook, still on his desk. It's there, he thought. Something we haven't seen. But we've looked everywhere. So we've seen the answer and haven't seen that it is the answer. And if we don't see it now, at this moment, we'll never see it at all...

'No offence, sir, but that's probably not a help,' said Cheery's voice somewhere in the distance. 'So many of the trades that use arsenic involve some kind of grease.'

Something we don't see, thought Vimes. Something invisible. No, it wouldn't have to be invisible. Something we don't see because it's always there. Something that strikes in the night...