If you ask, ‘Papa, how much longer?’ one more time, Detective Superintendent Roy Grace thought, I’ll throttle you! He glared in the mirror at his son, Bruno, right behind him, then at the satnav app. French names – towns, villages, roads. Every town, every village, every road. Except for the one road they wanted. Rue de Joigns.

Was there such a road at all, he was starting to wonder? Could they have been tricked? Might they be victims of an internet con man? A crook like one he had recently locked up? Surely not? Could he and Cleo have booked and paid for a week’s holiday in a French chateau that they were about to find out did not actually exist?

But of course it did! They’d looked it up on TripAdvisor, and it had loads of reviews, almost all positive. It was the rubbish satnav app on his phone that was at fault here.

Roy had started the journey in their rented car – a Citroën Space Tourer – in a very happy frame of mind. He was looking forward to this summer break in a gorgeous house in northwest France – and to rare quality time with his family. It might be their last family holiday for some while, as Cleo was now five months pregnant.

Yet something was starting to niggle him. It was like a darkness steadily rising inside him, just as the sky, loaded with rain, was steadily darkening outside. It was nearly 4 p.m. and it didn’t look as if there was going to be any evening sun today. The tall trees made the road seem even darker, more like night than a summer afternoon.

‘Papa, how much longer?’ Bruno asked.

Roy caught Cleo’s eye and saw she was grinning. She knew how much Bruno was annoying him. Actually, annoying both of them. And she was also pretty sure Bruno kept saying it on purpose – just to really piss them off. It was something the eleven-year-old seemed to like doing. One day, Bruno could put annoying people down on his CV as his hobby.

‘Not much longer, Bruno,’ Roy said. ‘It’ll be great when we get there, I’m sure.’

And it sure looked amazing in the photos on the internet. Château-sur-L’Évêque. A pool, tennis court, bicycles, beautiful grounds, deer park.

Roy took his eyes off the road for a fraction of a second, to glance again at Bruno in the mirror. But all he could see was the back of his iPad.