'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...
And there it was.
He blinked. The glittering stars of exhaustion were causing his mind to think oddly. Well, thinking rationally hadn't worked.
'No one move,' he said. He held up a hand for silence. There it is,' he said softly. There. On my desk. You see it?'
'What, sir?' said Carrot.
'You mean you haven't worked it out?' said Vimes.
'What, sir?'
'The thing that's poisoning his lordship. There it is ... on the desk. See?'
'Your notebook?'
'No!'