‘I’m not saying he’s a great guy who should be let off,’ Moore clarified. ‘Only that his preferred M.O. – cups of tea first, then shot to the back of the head while unobserved – suggests he might be uncomfortable with overt hostility. He wants people to like him – right up until the moment he shoots them dead.’

‘That’s … not a given,’ Simon changed course to end his sentence more tactfully than he’d first intended. ‘He might just be efficient, or risk-averse. Why allow your target to see you produce a gun and aim it at them when you can wait till their back’s turned and surprise them? If they’ve got even a split second’s advance warning, they might duck out of the way and then you’ve lost control of your kill.’

‘Wow. Spoken like a true scary murderer!’ Kerensa Moore laughed.

‘How do you think I catch these people year after year?’

‘Fair point, DC Waterhouse. You’re right: your analysis of Billy’s character is as likely as mine to be correct. It’s good to air as many as we can come up with. There might be other equally plausible possibilities. Let’s hear as many as we can.’

‘Yeah, let’s – later,’ said Simon, whose tolerance for Moore’s isn’t-it-all-jolly tone was fast evaporating. ‘I’m in the middle of recapping Angela McCabe. Like Linzi and Rhian before her, Angela also found a small white home-made-looking book, stapled in the middle, with no more than one word on each page. Together, the words added up to a line from a poem by Ella Wheeler Wilcox, an American poet: “Somebody’s baby was buried to-day”. Angela found the book in her handbag. Her husband said it was her favourite bag; she always had it with her. Anyone could have followed her and slipped it in at some point. After dropping her kids off at school, Angela was in the habit of going for a coffee at the Whole Foods Centre on Magnier Road in—’

‘Whole Foods Centre!’ Proust pounced on it. ‘And we’re expected to believe she’s not a hippy.’

‘The point is, it would have been easy for Billy to learn that Angela could be found there most mornings,’ said Simon. ‘At the Whole Foods Centre. Easy for him to be there too one day and slip the booklet into her bag.’

‘Also worth mentioning that Angela got a line from the same poem that Josh Norbury did, in his little white book,’ said Grace Woolston.

‘Norbury’s line was “And a shadow seemed drawn o’er the sun’s golden track”,’ said Sam.