An acronym: the letters standing for other words. ‘What’s it an acronym for? I never was much use at crosswords.’ He realised that she’d hooked him. He was interested, despite himself. But her voice had become faint, as though she were moving away from the door, forcing him to bring his head closer.

‘I’m going to kill you, Martin,’ she said, ‘the way I should have done right at the start in your flat. Don’t think I didn’t consider it. I could have put it down to a burglary. But it seemed messy at the time. It still isn’t a necessity, not now we have your friend Miss Watson. But I’m going to do it anyway.’ Her voice was very faint now. Hepton kept his head and body clear of the door, expecting a shot. None came. Then he heard the sound of exhausted breathing from along the corridor.

A thickset man had just reached the landing from the stairs. He was pausing at the top, trying to regain his breath. He stared along the corridor and saw Hepton.

‘What do you think you are doing there?’ he called. Then he started moving forward, quickly for his size. ‘This is Mr Devereux’s room.’

‘I know,’ Hepton said. The man moved towards the doorway, but Hepton gripped his arm with one hand and pulled him back, keeping the other tight on the door handle. ‘There’s a murderer in there,’ he said.

The man’s eyes widened; not in shock, Hepton realised, but in mild surprise only.

‘A murderer?’ The accent was difficult to place. Mediterranean? Eastern European?

‘That’s why I’m holding the door shut. She’s still in there.’

‘A she? And her victim?’

‘He’s in there too. Will you go for help, please?’ Hepton was becoming exasperated. Who bothered to ask questions when a killer was around? But the man made no sign of moving. He seemed deep in thought. Then, his eyes on Hepton, he reached into his trouser pocket and produced a tiny gun, so dainty that it might have been a trick cigarette lighter. It might have been, but Hepton thought otherwise.