Rachel Coakly and her younger brother John find themselves at the start of the main school holiday with nothing much to do. To make matters worse, they have completely lost contact with the friends that they made last summer, David and Sally. Rachel suspects that her arch enemy Robert Hagen is involved, and he has seemingly taken a peculiar interest in an obscure lost painting. Also, as a known anti-rail campaigner, is he responsible for the rather bizarre railway branch line closures that have happened over the summer? In a race against time, Rachel sets off with her computer whizz-kid friend Sarah and her arty brother to solve the riddle and track down their lost friends. But will they manage to stop the very last crucial railway line from closing before it's too late?