It's been a year since Kate and Tom became conductors on the Great Secret Intercontinental Railway, and life has changed completely! Delivering animal passengers to their rightful habitats using their very own secret steam train, The Silver Arrow, is exciting and magical and fulfilling. Until one day a new and mysterious train almost rams them off the track! Its name? The Golden Swift. Kate catches a glimpse of the conductors. They're children, like them, and they're dropping animals off at all the wrong stations! Kate is determined to catch up with their rivals and confront them. Her actions will lead to an adventure bigger than she could have dreamed of, racing through the highlands of Western Scotland, trekking in the Australian outback and diving down deep into the Bering Sea on a magical submarine. Kate will have to discover a whole new way to offer endangered animals safe and lasting homes …