Norah got up and went over to the window. The street below was deserted. She opened the window, trying to shake off her tiredness. She had stretched out on the sofa to think—and because her back had ached after sitting at her desk for so long. She must have fallen asleep straight away. Shivering, she closed the window.

She went into the kitchen. In the fridge were apples, yoghurts, ready-made sandwiches, plastic containers of salad. Things that demanded no preparation or effort—things you could simply shovel into yourself. For a moment Norah stared at the food as if she’d forgotten what you did with it. Then she took out a yoghurt and a sandwich and began to eat mechanically.

As she was eating, she heard the floorboards creak overhead—so Theresa was still up too. Norah jumped to her feet. She had to talk to someone. Now. She hurried into her clothes, reached for her keys, unlocked the door, stepped out onto the landing and dashed up the stairs—but stopped abruptly when she saw a young man coming out of Theresa’s flat. He locked the door behind him and turned to face Norah. It wasn’t the little idiot who’d shouted at Theresa—the one Norah had got rid of a few days before. This man was older than Theresa, closer to Norah in age, short and stocky, with reddish blond hair, watery blue eyes and a cleft chin. And he had a key.

He was clearly startled to meet someone on the stairs in the middle of the night, but said nothing—only nodded at Norah and tried to squeeze past her in silence.

‘Hi,’ said Norah. ‘Are you a friend of Theresa’s?’

The man stopped and stared at her, uncomprehending.

‘Theresa?’

Norah could feel her eyes narrowing to slits.

‘Yes,’ she said. ‘Theresa. The young woman who lives here.’

Something in his face changed. Then he smiled briefly.

‘Oh, I see,’ he said. ‘Theresa. Sorry, it’s just that I never call her that. Anyway, I must be going. Three in the morning’s hardly the time for a chat on the stairs.’

Again, he tried to push past Norah, smiling apologetically.

‘What do you call her then? Theresa, I mean.’

The smile vanished.

‘Is that any of your business?’

Touché, Norah thought. No, he was right, it wasn’t. Theresa, or whatever this guy called her, was old enough to do as she pleased—and give her key to whoever she liked.

‘I’m sorry,’ said Norah. ‘Is she in?’

‘No,’ said the man, finally managing to manoeuvre his way past Norah and setting off down the stairs at a leisurely pace. A moment later, she heard the front door slam shut.

Norah rang Theresa’s bell, but, unsurprisingly, nobody came to the door and she had no choice but to return to her own flat where the rusty smell of blood still hung in the air.

She sat down and went over what Werner had told her. He’d found out every detail of what Grimm had been doing at the time of Valerie’s death: what he’d been working on, what departments he’d been employed in, exactly where he’d lived. He’d been a lodger in an old lady’s house and this lady hadn’t forgotten the upstanding young man—a violinist like her youngest son, but also very handy about the house; a great help with repairs. Ever so quiet, apparently, and terribly hard-working and studious; he’d even found the time to give French and maths coaching on top of all his other work.