Rose threw herself to one side, tipping her chair over onto the floor, just as the gun went off with a deafening report. The recoil jerked Angela backwards and she gave a howl of pain and dropped the gun.

Rose sprang up from the floor. She fell on Angela, screaming and clawing and biting, dragging her out of her chair while Angela fought to get the gun. Angela was wiry and strong. She rolled Rose under her and her bony hands encrusted with rings fastened around Rose’s throat.

And then Harry erupted into the room, followed by Becket and Daisy. They had met Daisy in the street as she was running to get help.

Harry seized Angela by her thin shoulders and jerked her off Rose. He turned and addressed the gawping servants clustered in the doorway. ‘Fetch something to tie her up!’

‘No,’ gasped Angela. ‘I am calm now. I will go quietly.’

Two policemen came into the room. ‘Arrest this woman for murder and phone Detective Superintendent Kerridge. We will follow you to the police station and make statements,’ ordered Harry.

Angela stood up and with a quaint dignity said, ‘I must take my medicine with me. I have a bad heart.’

‘Send a servant.’

‘No, I have it here, over in that desk.’

She went to the desk and took out a small bottle. She squared her shoulders. ‘Now, I am ready.’

Rose looked wildly at Harry but he stared back at her, his face a mask. The two policemen moved forward. ‘If you will come with us . . .’ one started to say. Angela twisted the cork off the bottle and tipped the contents down her throat.

‘In a moment,’ she gasped. Her face contorted and she clutched her neck. Then she held her stomach and moaned as she sank to the floor.

‘She’s taken poison,’ said Harry. He turned to the servants. ‘Send for a doctor. Miss Levine, take Lady Rose into another room, for God’s sake. Lady Rose, there is blood on your dress. Are you wounded?’

‘One of the steels in my stays came loose,’ said Rose with a hysterical laugh. ‘You knew she was going to poison herself, didn’t you?’

‘You are upset and don’t know what you are saying. We will talk later.’

By the time Kerridge lumbered up the stairs, Angela Stockton was dead. He had taken half an hour to arrive, and in that half-hour Harry, Becket, Rose and Daisy had a hurried consultation to get their stories right.

‘I want to know what you have all been up to,’ said Kerridge. The four had retreated to a morning-room on the same floor.

‘Lady Rose is still shocked,’ began Harry. ‘Mrs Stockton held a gun on her and was going to shoot her. Miss Levine managed to escape and came to look for me. Fortunately we saw her on the street and came here immediately.’