This was a cheap ebook, and, as always, it's a bit of a gamble. Some are brilliant, some are awful, this was just a bit meh. There is a cracking story in here somewhere, but the authors have buried it under a positive mountain of cardboard cutout characters and unbelievable plot contrivances. The premise of mysterious goings-on at a research facility, ostensibly working on the common cold but actually up to something far more devious, is an intriguing one, and the plot rattles along at a good pace. But somehow, it never quite works.
The main characters are completely flat. Kate is meant to be a highly intelligent scientist but, frankly, she comes across as pretty stupid, not to say flighty. Paul is entirely nothingy. The bad guys are over-the-top cartoon characters. The minor characters are one-dimensional. The technique of allowing pretty much everyone to have a shot at being a point of view character, which should give them greater depth, actually manages to make them less interesting. In Sampson's case, seeing exactly what is going on in his head makes him less scary - Hitchcock understood that very well - and it removes a great deal of the tension by revealing pretty much everything that's going on. Even so, there's still pages of detailed explanation necessary at the climax of the book.
Vernon is a classic example of a missed opportunity. The authors could have made him a much more sympathetic character - Kate must have seen something in him at one time, after all, and he's described as being intelligent - but no, instead he's a one-dimensional bad-tempered misogynist whose only function is to be a mini bad guy early on and to create the dramatic climax by hiding away with Jack (and miraculously turn into a nice guy for the happy ending - bleah).
As far as the plot goes, there are a few moments of cleverness - the business with swapping the two boys is nicely done - but there are too many coincidences and contrivances all the way through. The car chase sequence is quite ridiculous. A stag? Oh please... And what was the point of the shotgun in the boot? There were moments, too, when I was distracted by some of the historical details. Would Paul really have been able to use a PIN and card to get £1000 from a cash machine in 1989, for instance?
There was one other aspect that grated on me, and that was the crude sexual descriptions. Sampson's fantasies I could live with (he's barking, after all), but Kate's panting lust felt all wrong, somehow. I couldn't quite see what the authors were aiming for. Sexual tension is a great driver, but that doesn't mean telling us every physiological response in Kate's body. It's not romantic or erotic, and frankly distracts from the thriller part of the story. It would have been far more effective and subtle to keep Kate and Paul's relationship in a more enigmatic state.
But overall, the story is moderately readable, with a nicely dramatic (if overdone) climax, and if you can overlook the flaws it's quite a page-turner. I'm feeling generous, so I've given it 3 stars for effort.