He lifted the rug and checked the floorboards but they looked as if they had lain undisturbed for years.

He sat down in an upright chair by the window and looked carefully around.

Downstairs, Lady Glensheil said sharply, ‘Where are

you going?’

‘I am going to my room to collect something, my lady.’

‘You will stay where you are until I give you

permission to leave.’

Upstairs, still in the lady’s maid’s room, Harry noticed a small strand of thread by the window. He got up and lifted one of the thick lined curtains, weighing it in his hand. He then went to the worktable and took out a pair of scissors. He deftly unpicked the deep hem of one curtain and shook it. An emerald necklace dropped to the floor, followed by a diamond brooch. He rapidly unpicked the hem of the other curtain and found a cameo brooch, an amethyst ring and a pearl bracelet.

He went rapidly downstairs to the hall and phoned Scotland Yard and left a message for Kerridge. Then he went to join Lady Glensheil. ‘You were right,’ he whispered. ‘Get a couple of your men to lock her up until the police arrive.’

Lady Glensheil signalled to a hovering footman. ‘I want two of you to take Thomson here and lock her up until the police arrive. Not in her room. The library will do.’

Thomson jumped to her feet. ‘Why are you doing this to me?’

‘You are a thief,’ Lady Glensheil said coldly. ‘Take her away.’

The guests sat as if turned to stone, some of them with teacups halfway to their lips as a screaming and protesting Thomson was dragged away.

Just domestic trouble,’ said Lady Glensheil. ‘Do not let it spoil my party.’ Rose looked across at Harry but he was talking intently to Lady Glensheil and did not seem aware of her existence.

She leaned across and said to her mother, ‘I have a headache. I would like to leave.’

Lady Polly smiled indulgently at Roger. ‘Would you mind escorting my daughter home?’

‘I would consider it an honour.’

It was then that Harry saw Rose. He hurried round the tables to catch up with her. Lady Polly watched him with furious eyes and just as he was passing her she thrust out her parasol and tripped him up.

Harry fell across the table, sending cups and glasses flying. He straightened himself up painfully because his bad leg was hurting. His suit was covered in jelly and cake. He hobbled quickly out of the room to catch up with Rose.

He was just in time to see her driving off with Roger. ‘Rose!’ he shouted, but his voice was drowned out by the sound of Roger’s car’s engine.

Thomson paced up and down the library, looking for escape. The library was on the ground floor and so the windows were barred.

She stopped her pacing and looked at the fireplace. She walked over and removed the screen and bent down. It was an old, wide chimney with climbing rungs for the chimney sweep’s boys.