‘In one sense, our confusion’s a good thing,’ said Sam. ‘We have new names and new faces, as yet unnamed, to consider: Kim Tribbeck, Sondra Halliday, this man at the comedy gig. Each new person we add to our list is someone we can take a DNA sample from, potentially – and maybe get a match with three of our four crime scenes.’

‘I want uniforms taking any samples from here on in,’ Simon told him. ‘Separate from any interviews we do – separate occasions altogether, I mean. The two don’t mix well if we want to establish trust.’

‘I didn’t realise your interviews were about establishing trust, Waterhouse.’ Proust chuckled. ‘I thought they were about making people want to jump out of the window.’

‘What if Kim Tribbeck’s not Billy, but this is still all about Kim?’ Gibbs said. ‘She gets a white book but she also gets to live. She gets hand delivery while the others don’t. She hasn’t got a best friend, but all the others have. She’s the special one, isn’t she?’

‘Different doesn’t mean special, Detective, whatever your primary school teachers told you.’

‘Has anyone read the book?’ asked Sam. ‘Beloved, Toni Morrison?’

No one had.

‘I’ll read it tonight,’ said Simon.

‘Good idea, Waterhouse. Run yourself a bubble bath and read a novel. That’ll help us.’

‘You know it will. That book was chosen out of all the ones that might have been sent. We need to know why.’ Turning to Gibbs, Simon asked, ‘What do we know about Kim Tribbeck’s life and anyone in it who might not be favourably disposed towards her?’

‘Or, turning it on its head, who might be,’ Sam said. ‘Kim’s alive and unhurt. That could mean Billy is favourably disposed towards her. She’s scared, I suppose.’

‘Not noticeably,’ Gibbs told him. ‘Her gran’s just died and somehow that’s left her scared of cancer and hospitals and illness, but not of being shot by a maniac. It sounded a bit too convenient when she said it, but I still can’t persuade myself she’s killed anyone. In terms of people in her life who might be of interest: estranged husband, estranged lover – she dumped them both. Sister of estranged lover’s worth looking at too. Her brother hid the affair from her because he thought she wouldn’t like it – saw Kim during the night when his sister was at work. Kim also has a brother she can’t stand, with whom she’s clashed big time over various family issues …’

‘Four excellent suspects full of juicy DNA, right off the bat,’ said Proust. ‘Good. Better.’

And not dismissed as far-fetched because not in any way famous, Simon noticed. How could you describe anyone as an excellent suspect with no idea of why a series of murders was happening?