RUBY PULLED THE BLOCK OF WOOD FROM THE DOORJAMB and took notebook 625 from its hiding place. The previous six hundred and twenty four, all varying shades of the same colour, were hidden under the floorboards. She had been writing things down in yellow notebooks since she was no more than four years old, when it had struck her that the smallest detail was what made up the whole big picture. RULE 16: EVEN THE MUNDANE CAN TELL A STORY. No one knew about the yellow notebooks, not even Ruby’s closest friend, Clancy. She wasn’t sure why she hadn’t told him; she just hadn’t.

      She flipped back to see what she had written over the last few weeks. There was a lot there, most of it still fresh in her mind, but she was hoping that there might be some detail that once re-read might mean more than perhaps it had when first jotted down. Some detail that made everything fit together, that revealed the pattern she couldn’t see. She sank back into her outsized beanbag and began to read.

      Her life as a Spectrum code breaker had begun in March, getting on for seven months ago now, and it had been no easy ride.

      Ruby, who was an ambitious kid, was determined to do more than crack codes: her lifelong dream was to be a field agent. That dream – and her life – had been almost snuffed out by various murdering thieves and kidnappers, but that only served to make her more determined. She had made it this far, she wasn’t dead, why give up now?

      It was the Cyan Wolf case that had led her to the blue-eyed Australian, and it was the conversation with her on Wolf Paw Mountain that kept circling her mind. She turned back several pages and read her notes on the case. It was up there on the mountain where things had taken an almost fatal turn, though in recent months things had had a habit of taking near fatal turns.

      Sometimes she thought she could still smell the fire that had burned around her, the forest catching light as she had dared the woman to explain her dark motives.

       ‘All this so you can make some money out of some stupid fragrance.’

      How the woman had laughed at that.

       ‘Is that what you think this is about? No sweetie, this is not about some high-end perfume counter cluttered up with rich folk wanting to waste their money. This is about something important, more important than you could ever imagine.’

      The woman had been talking about the Cyan scent, the scent of the Blue Alaskan wolf. A scent so rare that just a few drops were worth unimaginable riches, a scent with an irresistible pull – breathe it in and you fell under its spell. But the Australian had made it clear that she was not interested in it for its value as a perfume – she had far bigger ambitions.

      Ruby was chewing on a pencil and looking down at a blank page.

      She had been recruited by Spectrum in March to crack a code, just one. Her first (and supposedly last) assignment was to figure out what code-breaker, Lopez, had discovered before she mysteriously died. It turned out to be a plot to steal the priceless Buddha of Khotan. Thanks to Ruby’s work, the Buddha had been saved and the criminals identified. One incarcerated – Baby Face Marshall; one dead – Valerie Capaldi, aka Nine Lives; and one at large – Count von Viscount.

      It had all seemed to tie up quite neatly, everyone at Spectrum was satisfied, but Ruby was no longer feeling so complacent. Though the Buddha was now safely back in Yoktan (formerly the ancient city of Khotan), might it be that something had after all been stolen?

      Ruby wrote:

       Was something stolen from the Jade Buddha itself?

      She leafed back to the note she had made about the case when it had all been deemed over, done and dusted, put to bed.

       WHAT I DON’T KNOW:

       What was the Count looking at?

      She had seen him take out a small torch-like device and shine it into the eyes of the Buddha. What had he seen there? What secret might be held in the eyes of the Jade Buddha of Khotan?

      The case of the Jade Buddha was supposed to be her one and only code-breaking exercise, but Spectrum had kept her on, despite her age and despite LB’s reluctance to take on a mouthy school kid (the Spectrum 8 boss had been clear about that). Perhaps she hadn’t had much choice – even she could see that, had Ruby not been there, things would have ended very differently.

      Ruby turned to a fresh page and wrote:

       LOOSE END ONE: the jade.

      The second case had been a confusing one. The death of a Spectrum diver had turned out to be accidental, and some worrying pirate activity that had seen Ruby’s own parents taken hostage was in fact a cover to allow Count von Viscount to recover the lost treasure of the Sibling Isles. But on reflection this too turned out to be a bluff, a distraction – something much more sinister was going on. Clancy had told her just how pale the Count had turned when he discovered the vials of indigo he was carrying were smashed and his relief when he had found one, just one glass vessel, still intact. The indigo was the ink obtained from the cephalopod – a giant octopus sea creature – the stuff of legend and a legend no one (until then) had believed in. This indigo ink worked exactly like a truth serum – once ingested, you couldn’t help but tell the truth. Ruby had first-hand experience of its powers and could see just why any master criminal would want to have it sitting in his or her cupboard of villainy, but Ruby had a strange feeling that the Count had some bigger purpose for it.

      The pirates and their leader had been captured and marched to jail. The Count’s henchman, Mr Darling, had died in the strangulating grip of the octopus. But the Count himself, as always, had sailed away into the sunset, or in this instance into the dawn.

       LOOSE END TWO: the indigo. Was it acquired for some specific purpose?

      The third case was the Blue Alaskan wolf: rescued, but