‘Good. We’ll then tackle the first floor. Having cleared bedrooms three, four, five and seven, and bathrooms one and two, we’ll do bedrooms one, two and six, bathroom three and the linen cupboard. Again we make sure that all windows are secure, nailing up any that aren’t.’

‘I would suggest,’ said Bourne, ‘that we place threads and seals across all windows, in addition, and across front and back doors even if locked. Even,’ he added, ‘if we use these doors and it means unlocking, locking and resealing them from time to time.’

Pollard regarded him thoughtfully.

‘You mean, in case our friend has a key we know nothing about?’

‘Precisely.’

‘Look,’ Smith asked, ‘what’s all this business of sealing?’

‘It’s quite straightforward,’ Bourne replied. ‘You fasten thread across windows and doors with sealing-wax so that they cannot be opened without breaking the thread or dislodging the seal. The seals are impressed with signet rings so that they cannot be counterfeited.’

‘Like this one?’ The Captain removed a ring from his finger. He held the gold circlet up, almost as if challenging Bourne.

‘Yes,’ said Bourne. ‘Like that one. And this one,’ he added, tapping the ring he wore. ‘We’ll use both – on each door and window.’

Their eyes met and Paul read their unspoken addendum – and that way there’ll be less opportunity for trickery.

Pollard smiled briefly.

‘All right. We then tackle the attic floor.’ He consulted the plans again. ‘There are two stairs to the attics. We go up them, both at once, and work our way along to meet in the middle. And that should do it. If the man you saw, Mr Wilson, is still in the house, we’ll find him. And if he’s no longer inside, the precautions we’ll have taken should keep him out or at least let us know if he comes back in.’ Their eyes turned to the windows where flurries of snow still tapped with silent fingers. ‘If he can’t get in, he can freeze to death or make his presence known by knocking at the door.’

The search and sealing of the house took far longer than they had anticipated. The necessity to ensure that no one doubled round them and that each person’s securing of windows and doors was checked by another slowed up the operation.