Thirty-two minutes later I was inside Mill on the Floss, on the banks of a river next to Miss Havisham, who was observing a couple in a boat. The woman was dark skinned with a jet-black coronet of hair, was lying on a cloak with a parasol above her as a man rowed her gently downriver. He was perhaps five and twenty years old, quite striking, and with short dark hair that stood erect, not unlike a crop of corn. They were talking earnestly to one another. I passed Miss Havisham a cup of coffee and a paper bag full of doughnuts.

'Stephen and Maggie?' I asked, indicating the couple as we walked along the path by the river.

'Yes,' she replied. 'As you know, Lucy and Stephen are a hair's breadth from engagement. Stephen and Maggie's indiscretion in this boat causes Lucy Deane no end of distress. I told you to get the ones with pink icing.'

She had been looking in the bag.

'They'd run out.'

'Ah.'

We kept a wary eye on the couple in the boat as I tried to remember what actually happened in Mill on the Floss.

'They agree to elope, don't they?'

'Agree to – but don't. Stephen is being an idiot and Maggie should know better. Lucy is meant to be shopping in Lindum with her father and Aunt Tulliver but she gave them the slip an hour ago.'

We walked on for a few more minutes. The story seemed to be following the correct path with no intervention of Lucy's we could see. Although we couldn't make out the words, the sound of Maggie and Stephen's voices carried across the water.

Miss Havisham took a bite of her doughnut.

'I noticed the missing key too,' she said after a pause. 'It was pushed under a workbench. It was murder. Murder … by minotaur.'

She shivered.

'Why didn't you tell Bradshaw?' I asked. 'Surely the murder of a Jurisfiction operative warrants an investigation?'

She stared at me hard and then looked at the couple in the boat again.

'You don't understand, do you? The Sword of the Zenobians is code-word-protected.'

'Only Jurisfiction agents can get in and out,' I murmured.

'Whoever killed Perkins and Mathias was Jurisfiction,' she went on. 'And that's what frightens me. A rogue agent.'

We walked on in silence, digesting this fact.

'But why would anyone want to kill Perkins and a talkiag horse?'

'I think Mathias just got in the way.'

'And Perkins?'

'Not just Perkins. Whoever killed him tried to get someone else that day.'

I thought for a moment and a sudden chill came over me.

'My Eject-O-Hat. It failed.'

Miss Havisham produced the Homburg from a carrier bag, slightly squashed from where several Mrs Danvers had trodden on it. The frayed cord looking as though it might have been cut.