I'm finding bits of it depressing, but am still very involved in the story. There is a serial killer (well, at least this one's historical!) who's killing children in Cambridge, and the local Jewish population is instantly accused of ritual murder. Two are murdered and the rest take refuge in the local castle. The detective, Adelia, is clearly a stand-in for us modern readers who are appalled by 12th century England and its mores. She's been sent, along with a Jewish spy and a Muslim eunuch manservant, by the king of Sicily to find the real killer. It isn't made clear why the king of Siciliy has an interest, but I suspect money is involved. The king of England, Henry II at this period, is also appalled, because the Jewish population - "his Jews" - are a very lucrative source of tax money. When Adelia arrives, it's been a year since the first murder and three more victims have just been found. Luckily, she saves the life of the local Prior, which gives them an entrée into the local society so they can discreetly investigate.
I have no idea how accurate the forensic science in this book might be. It's given more plausibility by Adelia's training in Salerno, a renowned center of medical study that allowed women to practice and teach. For the purposes of the story, that's been enough for me. It's been holding my attention more than most of the books I've read lately.