Rob Townsend was daydreaming about Kirsty and the caravan, even as he sat at his computer going through the endless collection of electronic data that had been gathered from the remaining unchecked devices of Harry Roy, Morag Fairburn and Zayan Lal. After the conversation with Gillard, he had concentrated his search on Lal’s laptop and phone. The gold nugget he was looking for was one word: thallium, any mention of the deadly poison in an Internet search or on an email, prior to the death of Mrs Roy.

Lal had clearly been careful. The word did not occur at all at any time on any of his devices, neither in English nor Gujarati. Of course Rob still had to do the full investigation of the Gujarati texts and emails, some of which were encrypted in WhatsApp, to see what else had been said. That would take weeks. It was going to be a long slog and he couldn’t face it right now, so instead he decided to do the same basic keyword check on the accounts of Harry Roy and Morag Fairburn. He looked at his watch. With luck he could do both and still leave at the same time as Kirsty, 5.30 p.m. He set the desktop app searching for the word thallium.

It only took four seconds to flag up a whole series of hits.

Not on Harry’s computers, as he might have expected, but on Morag Fairburn’s home desktop PC. Townsend blinked, and looked again at the seven different searches over a period of four days. It included the Wikipedia page for the metal, a PDF of a pharmacopoeia describing the toxin’s effects on the human body and several other academic references which described real-life cases of thallium poisoning. The search had been conducted on maximum privacy settings, on a newly installed browser, which was then uninstalled at the end of the session. Most incriminating of all was a search for brand names of rodenticides in the Indian subcontinent and retail stockists.

If this had occurred in the last couple of weeks, it could be explained away as an interest in what had actually happened to Mrs Roy, given that the family were told she had been poisoned. But these searches were more than a year old.

The research intelligence officer could think of no conceivable legitimate interest that Morag Fairburn could have had in this knowledge. If it had been her work computer, it could be argued that someone else had used it. But at home?

Townsend picked up the phone and punched out Gillard’s mobile number. It was with regret that he realised he was unlikely to be able to travel home with Kirsty. In fact at this rate, if Gillard needed him to press on with the research, he might not even be able get away with her for the weekend.

Chapter 21

The discovery of incriminating searches on Morag’s home computer made Gillard even more determined to re-interview her quickly. She readily agreed that he and DC Michelle Tsu could come to her home that evening and, when he arrived a little before eight, he was surprised to find that she had prepared a spread of sandwiches and thick, gooey chocolate brownies.