Lost in the garden - Adam S. Leslie

Heather, Rachel and Antonia are going to Almanby. Heather needs to find her boyfriend who, like so many, went and never came back. Rachel has a mysterious package to deliver, and her life depends on it. And Antonia - poor, lovestruck Antonia just wants the chance to spend the day with Heather. So off they set through the idyllic yet perilous English countryside, in which nature thrives in abundance and summer lasts forever. And as they travel through ever-shifting geography and encounter strange voices in the fizz of shortwave radio, the harder it becomes to tell friend from foe. Creepy, dreamlike, unsettling and unforgettable - you are about to join the privileged few who come to understand exactly why we don't go to Almanby.