Tour guide Harriet Turner knows all about journeys. She's arranged hundreds of them for the travel agency her family runs. But when her work colleague and foster sister Lara disappears on the eve of a big overseas trip, Harriet finds herself in uncharted territory. Left in charge of a coachload of eccentric tourists on a themed tour based on the English TV detective series Willoughby, Harriet soon has her hands full. But as the bus wends its way through the picturesque countryside of Devon and Cornwall, the tour becomes another kind of journey for her. She finds herself facing big questions about her family, her childhood and her feelings for the guest of honour on the tour, the charming star of Willoughby, Patrick Shawcross. And the biggest puzzle of all: what has happened to Lara?