I had high expectations of this book because I loved some of the author's other thrillers (especially "The Surgeon" and "The Apprentice".Alas, this was a let-down.If I hadn't paid £3.99 for the book, I would have given up after two chapters. Various events happen, but they don't connect. There's no plot, no storyline, no one to root for, nothing to care about until fairly late into the novel. Eventually, some of the threads meet, but it takes ages before a story emerges.The characters are uninteresting. Most of them are so immature, I don't want to spend time in their company. And I don't mean the minors. The adult characters in this novel - people in responsible positions, such as doctor, police chief - have all the maturity of 13 year olds. The doctors bicker about has stolen whose patients, the police chief is curious and jealous, so he decides to interview the suspect (his lover) himself, ignoring protocol and common sense. The list goes on and on.What story there is - and I don't think I'm giving anything away here, because it's so utterly predictable - revolves around aggression spreading by infection, and teenagers are susceptible. Yeah, ok, so what? I've only read a dozen stories based on this premise. For a while I thought there was a virus making adults childish, which would have explained some of the idiocies, but no.The writing style is fluid, that's what I'm giving 2* for. The plot would have been 1*.But in places, even the writing style makes me groan. Whole pages are medical lectures. The author (through her characters) drones on and on and on, sorely tempting me to skip.Die-hard Tess Gerritsen fans may get some joy out of this. But if you're new to this author, it may be better if you read one of her other books first.