‘Do you think he always leaves it in a mess like this?’ Benwell said. ‘Or was he especially in a hurry this morning?’

‘He’s depressed,’ George said. ‘I don’t suppose he makes much of an effort.’

Benwell began searching in a methodical way and George, embarrassed by the official intrusion into Craven’s privacy, wandered through to the kitchen. The draining board was piled precariously with clean crockery and pans, a whole week’s washing up. There was one dirty plate and mug on the table, so presumably the cycle was about to start again.

‘There’s a letter here from his sister,’ Benwell called. He walked through to the kitchen with a sheet of blue paper covered in fine writing.

‘What does it say?’ George said. He preferred not to read it.

‘See for yourself.’

It was written when Kate Craven was at her happiest. She did not know how the affair had started, she wrote. Marcus had been such a figure of fun when they were young and now that she adored him it was as if he was quite a different person. She had no unrealistic expectations. She did not expect him to leave Olivia. But he spent most of his time in London anyway and she had no reason not to think that they could not be happy together for ever.

‘Are there any other letters?’ George asked.

‘No,’ Benwell said.

‘He must have kept this specially to fuel his anger.’

‘It’s proof anyway that Craven knew about the affair,’ Benwell said. ‘If he wanted to get his own back I wonder why he didn’t go straight to the press with the story.’

‘Because he cared too much for Kate’s reputation,’ George said, ‘even though she was dead.’ He felt an obligation to defend the man and realised that he was being persuaded by Molly’s arguments. ‘Why should he have wanted to kill Ursula?’ he said, almost to himself. ‘He had no quarrel with her.’

Benwell had begun to search through almost empty kitchen cupboards and did not answer directly. He knelt on the grimy floor and began to pull open dresser drawers.

‘What do you think of this, then?’ he said, standing up triumphantly, dusting down his trousers. George’s question was forgotten.

Underneath a roughly folded linen tablecloth was hidden an empty cardboard egg box and a hypodermic syringe.

‘That’s the evidence we need,’ he said. ‘We’ve got him!’

‘You’ll probably find traces of phosdrin in the syringe,’ George said slowly. ‘I’m sure that’s what Craven used to inject the eggs he used as bait on the hill. But there’s still no proof that he poisoned Ursula.’

Why had he kept the needle? George wondered uneasily. If he’d poisoned Ursula why hadn’t he thrown the thing away? Especially when he’d taken the trouble to return the empty jar of phosdrin to Vic Liddle’s shed.