'Yet they are under the direction of a complete stranger.'

'Don't be so territorial, Tegwyn,' said Stockdale, jovially. 'The inspector is no stranger to me. And if you think a Welsh murder can only be tackled by Welsh policeman, it rules me out. I'm as English as Cheddar cheese – and just as delicious. Now tell us what the post-mortem revealed.'

They were in Rees's surgery, a room as neat, chilly and sterile as the man himself. He consulted a sheet of paper before speaking.

'The cause of death,' he began, 'was heart failure brought on by a massive dose of sulphuric acid. Its corrosive properties can be seen in the disfigurement around the mouth and in several internal organs. The wound on the scalp and the bruising were caused before death.'

'I realised that when I saw the blood,' said Colbeck. 'As soon as the heart stops, so does the circulation.'

'Let me finish, please,' said Rees, tetchily. 'There were also bruises on the chest and arms of the victim, suggesting that someone may have been kneeling on him.'

'That disposes of your idea that the killer was a female,' said Stockdale to Colbeck. 'No woman would have been strong enough to hold him down.'

'She wouldn't have needed strength if he'd willingly submitted to being tied up,' returned Colbeck before giving Rees an apologetic smile. 'Do go on, sir.'

Rees clicked his tongue. 'Thank you,' he said with sarcasm. 'Need I remind you that I was the one who conducted the autopsy? All that you saw were the more obvious external signs. As it happens, Inspector, your wild guess has some foundation. The victim's wrists were tied tightly enough to leave a mark and there were similar weals on his ankles. In other words, he was spread-eagled on the bed.'

'That's what Inspector Colbeck suggested,' said Stockdale. 'He felt that Mr Kellow may have been seduced by a woman and that being tied up was part of some ritual.'