Foxglove Summer is the fifth book in the PC Peter Grant series by Ben Aaronovitch, and I believe the first book in which Peter spends the majority of his time not in London.
As the events of the last book have left Peter shaken, he jumps at the chance to spend some time outside of London. Unfortunately, the case he’s assisting on is a dark one: two pre-teen girls have gone missing in rural Herefordshire. There’s no indication that there might be magic involved, but that doesn’t stop for Peter from worrying. Time is running out.