'Still worth a mint. Go on, Strewth... get it out.'

They watched like cats as the pick pried loose more and more rock, and found an edge. And another edge.

Now Strewth's fingers began to shake.

'Careful, mate... there's a side of it...'

The men took a step back as the last of the obscuring earth was knocked away. The thing was oblong, although the bottom edge was a confusion of twisted opal and dirt.

Strewth reversed his pick and laid the wooden handle against the glowing crystal.

'Strewth, it's no good,' he said. 'I just gots to know...'

He tapped the rock.

It echoed.

'Can't be hollow, can it?' said one of the miners. 'Never heard of that.'

Strewth picked up a crowbar. 'Right! Let's—'

There was a faint plink. A large piece of opal broke away near the bottom. It turned out to be no thicker than a plate.

It revealed a couple of toes, which moved very slowly inside their iridescent shell.

'Oh, strewth,' said a miner, as they backed further away. 'It's alive.'

Ponder knew he should never have let Ridcully look at the invisible writings. Wasn't it a basic principle never to let your employer know what it is you actually do all day?

But no matter what precautions you took, sooner or later the boss was bound to come in and poke around and say things like, 'Is this where you work, then?' and 'I thought I sent a memo out about people bringing in potted plants,' and 'What d'you call that thing with the keyboard?'

And this had been particularly problematical for Ponder, because reading the invisible writings was a delicate and meticulous job, suited to the kind of temperament that follows Grand Prix Continental Drift and keeps bonsai mountains as a hobby or even drives a Volvo. It needed painstaking care. It needed a mind that could enjoy doing jigsaw puzzles in a dark room. It did not need Mustrum Ridcully.