Used book – Secret Clues, Fiona Kelly

Holly has just arrived in a small town in the London suburbs. It's not easy to make friends... What if she placed a classified ad in the high school newspaper? Something like: "Detective novel enthusiast, seeking fans to form the Mystery Club." Belinda and Tracy answer her ad: they too dream of tracking down crooks and killers! They set off in search of a supposedly lost original painting. But the investigation turns out to be much more difficult than they thought. And much more dangerous...