‘Toxoplasmosis. Yeah. They used to reckon that up to half the human population was infected with it. Most people never know they’ve got it inside them, but if you’re weak, with a bad immune system, or, like, a baby, it can kill you, or make you blind, or give you brain damage.’

‘You saying I could have it and not know?’

‘Yeah. Some people never have any symptoms, or they might just think they’ve got, like, flu, or something.’

They reached the stairway that led down to the ground.

‘You trying to tell me that’s what the disease is?’ said Blue, starting down the stairs. ‘It’s a kind of toxoplasmosis?’

‘Come on, we ain’t got all night.’ Achilleus pushed past the two of them, impatient with the slow progress that Skinner was making as he waddled along, limping slightly. Blue noticed that he was wearing no shoes and that his feet were covered in thick layers of leathery skin.

Skinner waited for Achilleus to get ahead and then carried on explaining things to Blue.

‘Not toxoplasmosis,’ he said. ‘Something similar. We call it the Nightmare Bug. The way it works, though, is just like toxoplasmosis. So you can get infected without knowing it; you can carry it for years without any symptoms, and it can affect your brain, change you completely.’

‘Can toxoplasmosis do that?’ asked Blue, getting worried that there was one more thing in the world to stress about.

‘You can catch toxoplasmosis from touching cat crap,’ said Skinner. ‘Or soil where a cat crapped, the parasite can live there. Then if you don’t wash your hands it can get inside you, where it’ll breed. The thing is, once it’s in you, it can cause you to behave differently. If mice get it, for instance, they’re not scared of cats any more.’

‘You’re joking me?’

‘No. It’s true. A mouse with toxoplasmosis will go looking for cats. They’re attracted to their wee, I think, and they’ll go up to them without any fear.’

‘What? It makes mice become supermice and attack cats?’

‘Kind of. The parasite controls their brains. So they go up to cats and … and, well, they get eaten. So the parasite gets into its main host. The cat.’

Blue stopped and Skinner turned to him.

‘And people that have the toxo?’ Blue said, looking suspiciously at Mrs Jones, who was still tucked up inside Skinner’s jacket. ‘Are they attracted to cats too?’

‘Not as far as I know,’ said Skinner. ‘But it can cause depression, mental disorders, even suicide.’

‘That is bad news,’ said Blue. ‘I wished you hadn’t told me that.’

‘Sorry. I was only trying to explain.’