‘Thank you.’ Isobel took her coat off. ‘I’ll just put this in my room and I’ll be back down right away to set up the breakfast things.’

Ursula nodded, and as Isobel put her foot on the first step, she smiled to herself.

A few seconds later there was a gasp. Ursula waited.

‘What has happened to my door?’ Isobel ran back down the stairs. ‘It’s locked and I can’t get in.’ Her voice began to break. ‘Is this because of the jewellery box? I explained about that and I am so, so sorry.’

‘Oh my goodness, absolutely not!’ Ursula reached into her pocket and pulled out a shiny new brass key. ‘This is for you. We all thought that as you are part of the household here, part of the family, really, you should have your privacy when you want it. I would never dream of coming into your room without permission, but after everything that happened before, we thought you might like to be sure of that.’ She offered the key to Isobel. ‘Although you probably won’t want to lock the door when you are actually in the room, in case there is an emergency or something.’

‘A fire.’

‘Yes, a fire. But when you’re up there, I thought that rather than shouting up as though you are a naughty child, I could use this instead?’ Ursula pointed to a small brass door knocker which had been mounted on a piece of wood and fixed above the hand rail at the foot of the staircase.

Isobel took the key. ‘Did the person who fitted the lock take the old one away?’

‘It’s outside. Finlay is fascinated by things like that and I thought he might want to take it apart and see how it works. It’s on the scullery windowsill.’

Isobel fetched the old lock. ‘Let me show you something.’

‘What am I looking at?’

‘She had the lock changed. It’s not the one that was on the door to start with; that one was taken away when Mr Black was on a trip somewhere, and this one was fitted instead.’

‘Why would she do that, if she intended to stuff it with paper?’

‘That happened later. Look at the lock. You can only lock it and unlock it from one side, see? The keyhole the other side has been blanked off.’

Ursula frowned. ‘I don’t understand.’