They followed the path marked out for them to climb the stairs and reach the master bedroom. The victim’s body still lay where PC Myers had found it, half on and half off the rug, twisted at an unnatural angle. She looked as though she’d been turning towards the door, one arm outstretched, but bent awkwardly by the fall. The red stains on the sheepskin ran on to the carpet and soaked the victim’s nightdress. Cooper noticed that the nightdress was blue, only a shade or two darker than Abbott’s crime-scene suit.

The bedroom was noticeably cooler than the rest of the house. And there was an obvious reason for that – the casement window stood open. A cool breeze blew through the back garden of Bain House, and a few dead leaves had drifted on to the window ledge.

‘So,’ said Kessen. ‘Three shots, you said?’

Abbott stood over the body. ‘Well, two shots hit the victim. The medical examiner says either one of them might have been enough to kill her. Certainly enough to put her on the floor.’

‘So where did the third shot go?’

‘That was a miss. The bullet embedded itself in the bedroom wall there, high up near the ceiling. See it?’

‘Yes.’

‘We’ll be able to give you an idea of the weapon once the bullets have been recovered.’

‘Time of death?’ said Kessen, without much sign of optimism.

‘Between thirty and forty hours ago, according to the ME. Rigor mortis was almost gone when he examined the victim, but for a bit of residual stiffness in the abdomen.’

‘My God, forty hours?’

‘At the maximum.’

Hitchens looked at his watch. ‘That would put the earliest time of the incident at nine p.m. Saturday. And the latest at seven a.m. Sunday.’

Kessen shook his head. ‘For heaven’s sake, how does a woman get herself shot and then lie dead for nearly two days without anyone noticing? Why didn’t someone somewhere miss her? Why didn’t they get worried when she wasn’t out and about doing all the things she usually did?’

‘The time is just a temperature-based estimate, of course,’ said Abbott. ‘You’ll need some other evidence to pin it down more closely.’

‘Yes, thank you.’

‘Well, temperature-based methods of calculating time of death are the most prone to error, you know. Newton’s Law of Cooling isn’t the most modern approach.’

Ah, Newton’s Law of Cooling. It was a familiar phrase, one that had stuck in Cooper’s mind from his training. When he first heard of it, he’d pictured some seventeenth-century eccentric sitting under a tree with an apple bouncing off his head. He didn’t know the mathematics behind Isaac Newton’s theory, but he knew it was almost always inaccurate – hence the medical examiners hedging their bets and stretching out time scales like Play-Doh.