Laura was disappointed and also a little relieved. It wasn’t like she’d wanted to find some sort of macabre torture chamber. It was more that she’d hoped to prove Doyle wrong, show that the taxi driver might have taken Mary Ellen and it hadn’t been fair to assume she’d done a flit.

Ray studied her face. He’d seen her enthusiasm and resolve ebb as they’d combed the house and found nothing. He hadn’t even met this Doyle character and he was still on Laura’s side.

It was then he had the light-bulb moment.

‘I have a confession to make,’ he said, just as she opened the front door.

‘Excuse me?’

‘My true blue Dublin blood is not as pure as I make it out to be. My granny on my mother’s side is from Roscommon.’

‘Roscommon? Jesus, Ray, you don’t get more culchie than that.’ She smiled, bemused. ‘And why are you revealing this sordid secret?’

‘We used to visit there when we were kids. I remember the cottage. A little like this one, as it happens. It had a big open fire in the kitchen that she used to light every evening, winter or summer. I remember sitting on the hearth as she rocked in her chair drinking Guinness – for the vitamins and the iron, of course. My job was to sweep up the fragments of logs and turf that had been spat out onto the stone floor. Laura, who puts carpet in a kitchen? Especially a country kitchen with an open fire?’

Laura blinked. ‘Not anybody I’ve ever known.’

Ray led the way back into the kitchen. The light was fading fast and it had grown cooler. The storm, the culmination of weeks of unusually hot weather, had finally broken. Rain lashed against windows that had probably withstood much worse but still seemed on the verge of caving in.

The vacant building had suddenly become more ominous – the possibility of a hidden space beneath the floor of the once homely cottage unnerving both detectives.

Ray flicked the light switch in hope, but nothing happened.

‘I can’t believe we’ve been complaining about all that sunshine,’ he said, dropping to his knees inside the door. He felt the edge of the carpet along the wall under the skirting.

‘It’s tacked, but loose,’ he said. ‘I should be able to …’ He grunted as he pulled, eventually freeing the dog-eared fabric from the floor.

‘Got it.’

They knelt on opposite sides of the carpet and began to roll.

As each inch of the original cold stone floor was revealed, Laura felt her nerves steady. How likely was it that a cellar lay under this solid mass? The taxi driver had only rented this accommodation. He was hardly ferrying in cement-breaking machinery and tunnelling into the ground.

And then, suddenly, it was there. A square wooden trap door, at their fingertips.