Jem had a thousand questions, but Rosie was up and moving, speaking urgently into her radio as she ran back to the kitchen. She returned within seconds, carrying a dilapidated knife block and the stone.

“We need to jemmy it,” she said, flinging out a carving knife and a long, thin sharpener. She fitted the latter into the loop of the padlock and used it like a lever, changing her angle of approach repeatedly as she felt for a weak spot. Jem took the stone instead and bashed it into the slats. The shock of the blow reverberated up her arms, but she’d sheared off a chunk of wood that flew past Rosie into the hall.

“Right. Brute force and ignorance it is,” Rosie said. She adjusted her grip on the knife sharpener so she was holding it like a spear and aimed it between the slats. “Get clear of the hatch!” she yelled, stabbing the sharpener into the crease as Jem resumed her indiscriminate hammering. The boards began to bow beneath the combined onslaught, cracks appearing at random, before one entire length snapped cleanly in the middle. Rosie joined Jem to stomp on the weakened planks, until their boots smashed a hole large enough for them to climb through.

“There’s a fixed ladder,” Jem said, tapping the top rung with her toe and then pressing harder to test its integrity. The ladder squeaked and juddered beneath the pressure, but it seemed robust enough.

“Do you want me to go first?” Rosie asked.

Jem shook her head and grabbed her response bag. “I’ll see you down there.”

The smell was the first thing to hit her, a foetid cocktail of human waste and wet rot, undercut with a trace of vomit. She breathed through her nose, acclimatising to the stink, and panned her torch around as she reached the bottom of the ladder. The light picked out an empty water bottle, the wrapper from a loaf of white bread, crisp packets, and a roll of toilet paper. She found the children in the farthest corner: two girls huddled beneath a blanket, their hands raised to shield their eyes. They were filthy and shivering and obviously traumatised.

“Please don’t hurt us,” one of them said. Her voice was hoarse, as if she’d been screaming for days. Wincing, she licked her chapped lips and tightened her hold on her friend. “We didn’t do nothing wrong.”

“We’re not going to hurt you,” Jem said. She took a cautious step, aware of Rosie a couple of paces behind her. “I promise we’re not going to hurt you. My name’s Jem and I’m a paramedic, and Rosie here is a police officer. You’re safe now, okay?”