‘Revenge, no. Self-preservation is perhaps understandable.’ At my silence, he continued, ‘Watson, as I have said before, I do not exist to supply the deficiencies of the police.’

‘Yes, you do.’

‘In any case, I think I shall leave Madame to them.’

‘Well, it is fortunate for Deacon Buttons that you did not do so in Cambridge. He might have hanged for a crime he did not commit. Or ended up in the clutches of Lamb.’

Holmes smiled and adjusted the cushions. He looked about to doze.

‘Holmes, on another matter. I’ve brought this up twice to no avail. I’m going to pay that Lossop a visit today. With or without you.’

His eyes opened sleepily. ‘Oh, that won’t be necessary, Watson,’ he said. He closed his eyes. ‘That package on the table there. I assisted Mr Lossop last night against a rather formidable threat. He is now safely en route to Peru. But your box … have a look.’

I was already at the table, tearing off the brown paper. Inside was the mysterious silver box! It gleamed attractively in the morning sunlight, its Celtic dragons looking nearly alive. The lock had been sprung and it was open a crack.

‘You have not looked inside, Holmes?’

‘Of course not.’

I paused, staring at the thing. Something kept me from lifting the lid. Something I didn’t expect. A kind of dread.

‘Watson, you hesitate. Perhaps you might consider holding off,’ said Holmes quietly.

‘Then you have seen what is in there!’

‘No. But think of this. You have long since put to rest whatever family drama caused this extraordinary act on the part of your mother. It troubles you greatly. I might have ferreted it out, dear friend, but I have left you your privacy—’

‘You had better!’

‘Consider the difficulty for your mother to procure such a unique and unassailable item as this box. She must have given you or sent you the key.’

‘How could she? She died two days after she gave this to Elspeth Carnachan!’

Holmes sat up, awake now, and looked around for his pipe.

I turned back to my box. Again, I hesitated.

‘The design of this box, the letter to be held for later delivery, all this smacks of planning, detailed planning,’ said he. ‘All the more reason to think she gave you the key. How did she die, Watson? You have never said.’

I put my hands on the box, feeling its cool, smooth surface so lightly engraved.

‘Watson?’

‘Ah? Oh … my mother. She drowned. Oddly very near where Rose had drowned three years earlier.’

I felt his eyes upon me. ‘Rose?’

‘My twin. We were both six when Rose died.’ I said. ‘Drowned as well.’ I felt suddenly naked, exposed. ‘I think I shall ask for more coffee. Would you like some more coffee?’