‘That’s what the lady bought.’ The apothecary pointed to the tank. ‘Sulien water-snake venom. My most expensive remedy.’

‘She bought venom?’

‘She had a prescription. It was all perfectly legal, I assure you.’

‘And what is this venom prescribed for?’

The apothecary seemed reluctant to explain.

‘Certain physicians here regard the treatment as their secret. If word were to get out…’

Acir brought out another two gold courons and laid them on the dusty counter.

‘Administered in minuscule doses, it is the most efficient pain-killer. When laudanum and the poppy drugs cease to be effective, water-snake venom can bring relief.’

‘But what ails the lady?’

‘Megrims. Very severe megrims. The physicians only prescribe the venom in the worst cases – because of the risk.’

‘What risk?’ Acir heard the edge to his voice.

‘A bite from one of these creatures can fell a full-grown man in a matter of minutes. The venom is injected through the front fangs. It numbs the prey almost instantly. So it’s tricky trying to milk the slippery little devils. See?’ He put the scoop into the tank and instantly the water became a wild froth as the water-snakes seemed to go into a frenzy, attacking with their teeth and their tails.

Acir drew back but his clothes were already spattered with water.

‘And is there no antidote?’

‘None. If they were to bite me, my head would soon start to spin, my sight would blur, my breathing would slow – I’d be dead within hours. So I keep ‘em well-fed.’

Fiammis a sufferer from blinding headaches? He could never once recall her complaining of the megrim. What did she want with such a lethal poison?

A chilling suspicion began to form in his mind. The dusty little shop seemed suddenly airless; he had to get out.

‘I could furnish you with more details if you so wish…’ the apothecary called after him.

Orial went running up the steps to the Cabinet of Curiosities, eager to tell Jolaine Tradescar of Khassian’s discovery. But when she reached the door she saw that a sign had been placed in the window, proclaiming:

‘Museum closed until further notice for renovations’.

‘Jolaine! Jolaine!’ Orial tried the door handle: it was locked.

‘What’s amiss? Is the building on fire?’

Orial heard Jolaine’s voice, sharp with irritation, from deep inside the Museum as her shuffling footsteps came nearer.

‘I’m very busy. I haven’t the time –’

Heavy chains rattled against the door panel as the Antiquarian shot the last bolt and opened the door, peering suspiciously with light-starved eyes into the sunshine. For one moment, Orial was irresistibly reminded of a mouldiwarp poking its snout out of its burrow.