ELEVEN

      I

      Walters had been so intent on catching the BMW that he’d neglected to memorize its licence number. ‘The plates,’ he said, whirling around on Pete and Kieran. ‘Tell me you got their plates.’

      ‘I did,’ said Pete, jotting the number down before he could forget it.

      ‘That was him in the passenger seat,’ muttered Kieran. ‘The one from the old bat’s house.’

      ‘I know.’ Walters clenched a fist. He’d thought he’d been so smart setting that fire. He’d taken it for granted that the police would have nabbed Luke by now, would be scoffing at his story, preparing charges of manslaughter and arson. Instead, he now had the girl and the driver as witnesses for his defence; and even their tame policeman had become a liability, a thread that could be followed back through his boss, first to Croke and then to them. Walters looked at him. He was standing open-mouthed in the road, radio in hand, evidently wanting to call it in but not knowing what to say. Walters marched over to him, clapped him on his arm. ‘Good work,’ he said. ‘If you still want to join us, I’ll put in a word for you.’

      ‘Yes,’ said the policeman uncertainly. ‘Thanks.’

      ‘And keep all this to yourself, right? National security. Above even your boss’s clearance. Can’t say any more. Not until you join us.’ He flashed him a smile, strode to the SUV. They all piled in and pulled away, leaving the policeman still standing there dumbly, doing his best mannequin yet.

      ‘What now, boss?’ asked Pete.

      ‘We find that BMW and get rid of that fucking email.’ He turned to Kieran. ‘How much of her password did you get?’

      ‘First six characters. Should be enough to break the rest.’ He set a programme running, turned to Pete. ‘Give us their licence number, then.’ He tapped it in, ran a search. ‘It’s a rental,’ he announced, thirty seconds later. ‘Company called Jonson’s Cars.’

      ‘Where are they?’ asked Walters.

      ‘Head office is St Albans,’ said Kieran, checking his screen. ‘But they’ve got a dealership here in Cambridge.’

      ‘Open Sundays?’

      ‘For another hour.’

      ‘Then give me their address. Let’s pay them a visit.’

      II

      ‘What now?’ asked Pelham rhetorically. ‘What do you mean, what now? You check for your aunt’s damned email.’

      Rachel nodded. She logged in on his phone and there it was.

       ‘My dearest Rachel,

       The most extraordinary thing – some Isaac Newton papers have just been unearthed in my attic! It seems your Great-great uncle Bernard bought them at Sotheby’s for next to nothing, and now they’re worth a small fortune! And we always thought him the unworldly one! Anyway, I thought of you and your brother at once. Bernie doted on your mother, though she wasn’t much more than a girl when he died. I’m sure he’d have wanted to help.

      Now this is all supposed to be terribly hush-hush, but apparently some terrifically wealthy collector is about make me an offer. Naturally I haven’t the first idea what the papers might be worth, and the nice young man who found them will only say they should fetch £20,000 or more. That would be wonderful, of course, and I