Her eyes widened slightly and she stared at the photograph of the dreaming face. The familiar face. The family face. Silently she trailed a forefinger around the cut-out line of the photograph.

‘Thank you for your sensitivity, Joe. How like you to have censored the rest of the . . . unpleasantness. It must have been . . . unpleasant.’

‘Can you confirm that this is Marianne? Your older sister?’

‘Of course. But there were others. What have you done with them?’

‘I have them safe and they’ve been doctored in the same way. I was going to reassure the subjects that all danger has passed from them but . . .’ He paused and held her gaze. ‘I can’t do that until the negatives are in my possession or, at the very least, I am confident that they have been destroyed.’

‘They have been destroyed, Joe.’

He waited, willing her to go on.

‘They were handed over to me and I put the evil things on the fire,’ she said finally. ‘They made a fine blaze.’

‘I’d be interested to know how they made their way into your hands?’

‘I’m sure you would. “Still ferreting,” Bill would say.’ She smiled. ‘When they give you a knighthood you can have it for your motto. You must let me devise your coat-of-arms.’

Joe grinned. ‘What do you see? A ferret rampant gardant and above, a scroll saying semper vigilans?’

‘Something like that. Well, Mr Ferret, the negatives were brought to London by that scheming Audrey. She was intent on raising money to finance an idle future by selling them to me for whatever she could get.’

‘I think Audrey had something even more valuable to sell to you,’ suggested Joe.

Tilly smiled as though acknowledging an opponent’s clever chess move. ‘My life or liberty, you mean? Yes, that. She recognized me the moment I took off my hat at King’s Hanger. Though I didn’t register her as anything other than a maid, she saw me going into the Dame’s room. As she said, she was interested to catch a sight of Bea’s latest conquest! She lurked about and watched me come out later . . . much later . . . and go down in the lift.’

‘And your presence could perhaps have been explained away when she realized you were a policewoman . . . had it not been for one extraordinary fact.’

Tilly nodded and looked down at her plate.

‘You went into the Dame’s room wearing a black lace dress and black gloves and emerged in a silver-grey dress – a bit long for you and hitched up at the hips with a silver belt – and a pair of spanking clean white gloves. Perhaps Audrey even recognized the dress – it was one of her mistress’s best. She had been planning to wear it at the Savoy the next night.’

‘When we interviewed Audrey she managed to make it quite clear that she understood what had gone on and I made the opportunity to speak to her alone.’

‘Ah, yes. While I was dispatched to admire the tulips.’

‘I agreed to whatever she suggested. I told Bill . . .’

‘I conveniently sent you both off into the orchard to compare notes,’ sighed Joe. ‘You told him everything, didn’t you? About the Dame and her treacherous intentions . . . the Hive . . . Donovan . . . the lot!’

‘I confided in Bill, yes. I was very sure I could trust him.’

‘Your trust was well founded. He protected you well. And I think you persuaded him to deal with Audrey?’

‘Yes. He rang her when we got back. He . . .’ she hesitated, ‘dealt with everything and handed me the negatives afterwards.’

‘Don’t be so mealy-mouthed, Constable!’ Joe’s voice hardened. ‘He lured her to Waterloo Bridge, grabbed her bag and threw her into a cold, dark, fast-flowing, filthy river where she drowned. You made use of Armitage.’

Tilly breathed deeply. ‘You’ve worked it out, Joe. You know perfectly well we used each other. Had to! Had to!’

‘It must have been quite a stand-off, the two of you facing each other over the Dame’s dead body – or was she still in her death throes?’

‘Death throes, I think,’ said Tilly, unperturbed. ‘I was determined to have it out with her. She’d killed my sister with her foul corruption and blackmail! We all thought Marianne was grieving still for our mother but she didn’t get over it. She got worse in fact. Depression, flashes of temper, strained silences. We couldn’t understand what was wrong with her. One day I found her dead in her bed. An overdose. Looking very much as she does here,’ she said, gently touching the photograph on the table.

‘She’d left a letter for us. Explaining all. Father was beside himself with rage and grief. I had to stop him from rushing out with his gun. No, there are better ways, I told him. More people involved than us: the other victims, the country itself. It needed our discretion. We decided to take it to the very top. And I think they listened to Father. But we waited and waited and nothing seemed to happen. I suppose they were investigating her. Then it became evident that they were taking the easy way out. The creature was going to be allowed to get away with a rap on the knuckles and an early, discreet retreat from public life.

‘I hadn’t intended to kill her. I’m sure I hadn’t. I didn’t take a gun or a knife or a dose of cyanide with me. I meant to confront her with her crimes. I’d seen her making eyes at Joanna and I thought, “Oh, Lord! She’s not given up! It goes on!” I had a quiet word with Joanna in the powder room and advised her to leave there and then. She was bored out of her brains by that stage and very pleased to take my advice.’

‘So, you went up in the lift after all – in your black dress, you did not, at that stage, answer the description the lift boy was given – if indeed Armitage bothered to ask him . . . I have long ago discounted any evidence provided by the sergeant. I expect the Dame was very surprised to see you instead of her chosen prey when you walked in through the open door a minute or two after she let herself in.’

‘She was furious, in fact, with me for interfering! I told her who I was, which made her even angrier. I informed her that my sister had confided everything before she killed herself. I told her that she was under surveillance and her days were numbered. Any naval man she encountered was silently observing her, despising her for the traitor she was. I laid it on thick! An avenging angel, you’d have said. I wanted to see her squirm. She went quite mad. She’s . . . was . . . a frightening woman when she was angry. You saw on her dead face the faintest echo of what she was capable of. Well, I’d over-steered. She picked up the poker and hit out at me. I dodged and she tried again. I dashed about the room, fearing for my life. She cornered me over by the fireplace. I was so desperate by then I wrenched the poker from her . . . I’m stronger than I look, sir, and I’ve got used to tackling reprobates.’

Joe nodded. ‘Seen you in action, Westhorpe. And then?’ Urging her on towards the hardest part of the confession.

‘I hit her on the head. I thought I’d just stun her. But once wasn’t enough! She wouldn’t die! I had to keep hitting her. The blood splashed everywhere. I never heard Armitage climb in until he shouted in his police voice, “Put down that weapon, miss!” Well, I stood for a while pulling myself together. I was covered in blood by then and she was moaning and dying on the floor. But my senses were unbelievably sharp, sir,’ she added wonderingly. ‘At a moment like that, people in books – and in the dock! – say, “I was confused, mad, didn’t know what I was doing, out of my senses.” It’s not like that. I was very much in my senses. Seeing everything with perfect clarity. I looked at Armitage. He had a nice face. Looked dreadfully concerned.’ She smiled. ‘But I did wonder what he was doing up on the roof at that time of night, climbing in through a window, and I guessed.

‘He took off his glove and put a finger to her neck to check for life. “She’s a gonner,” he said. I solemnly surrendered my weapon. I handed him the poker, sticky end first, and he took it automatically, then, realizing what he’d done, he dropped it as though it were white hot. I grabbed it and threw it through the window. We heard it clanging down over two floors. Impossible to find it in the dark.