'How did she get hold of it?'

'Exactly,' said Colbeck.

'According to medical evidence, it was sulphuric acid.'

'Do you have many chemists and druggists in Cardiff?'

'Well over a dozen,' replied Stockdale, 'and many of them are in Butetown. There are people there who don't ask questions of their customers. They just give them what they want. It's the reason we had three poisonings in the district last year.'

'Mr Pugh was warning me about the perils of Butetown.'

'It can get lively,' conceded Stockdale with a grin, 'but that's part of its charm. Archelaus Pugh wouldn't venture anywhere near the docks without an armed guard but I know my way around. It was also the sight of one of my early triumphs. It must be almost fifteen years ago now,' he recalled with a nostalgic smile. 'A number of sea captains had been assaulted and robbed near the West Dock. So I dressed up as a sailor one night and acted as bait.'

'That was a bold thing to do, Superintendent.'

'Luckily, it worked. When I saw that three men were following me, I broke into a run and they gave chase. One of them was much faster than the others and got well clear of them. I stopped, punched him on the nose and knocked him to the floor. Seeing what I'd done, his friends turned tail.'

'What happened to the man himself?'

'I arrested him, charged him with robbery and sent him for trial. He was transported for seven years.' He gave a throaty chuckle. 'I was in court to savour the moment.'

'I hope that we'll both be able to savour the verdict that's passed on the killer.'

'Whether it's a man or a woman,' remarked Stockdale.

'Or, indeed, both,' said Colbeck. 'If two people were involved, they are both culpable and will end up side by side on the gallows.'

'It's where they deserve to be, Inspector.'