He licked his lips nervously. He knew, just as Wada knew, that he could only release her once. From that moment on, he’d have to trust her to keep her word. And she knew, just as he didn’t, that she hadn’t decided yet whether she would.

She said nothing. She waited, her instinct for patience winning out over the temptation to press him further. He stood, looking down at her. He dried his lips with the side of his hand. He adjusted his glasses. Then he reached into the pocket of his trousers and took out the key to the handcuffs.

She didn’t move as he knelt awkwardly beside her. She had to let him do this of his own volition. It had to be his decision.

He grasped the cuff attached to her right wrist and twisted it towards him to reach the keyhole. Then … he hesitated. ‘I … I’m not sure,’ he muttered. ‘Perhaps … it’s safer … to leave things as they are.’

Wada saw the change in his eyes and knew at once. He wasn’t going to let her go. She’d brought him to the brink. But now he was edging back.

The key was close. The chance was there. And it wouldn’t last longer than a few more seconds.

She plucked the key from his fingers. ‘No,’ he shouted. She rolled under the basin, twisting the cuff round the downpipe to evade his grasp. He lunged after her. But already she’d slid the key into the keyhole. One turn. And she was free.

Caldwell tried to pin her against the wall. He grabbed at the cuff that was still in her hand, banging his head against the underside of the basin as he did so. He was dazed for an instant. It would have been enough for Wada to escape. But there was a way to make her escape more certain and she took it. She closed the cuff round Caldwell’s wrist and snapped it shut, then scrambled away from him across the floor.

Caldwell tried to go after her, but the handcuff chain clanged taut and he fell on to his elbow with a grunt of pain, then rolled on to his side. ‘Stop, stop,’ he cried. ‘I’m sorry. I shouldn’t have done that.’

She wasn’t listening. She slipped the key into her pocket and dodged past his flailing feet to the door.

‘I’m sorry, I’m sorry,’ he mewled on. ‘That wasn’t meant to happen.’