Bear Hoskins steps in at the eleventh hour to replace an injured colleague and help supervise Princewood School's exchange trip to Germany, enticed by a visit behind the former Iron Curtain and an opportunity to indulge his unusual fascination with borders. What the history teacher does not realise is how his humorous, engaging public speaking skills will lead him to a mystifying hunt for a long lost relative and a bizarre tale of defection from the Cold War era. Just before leaving, he meets newly qualified vicar, Laura Branscombe, whose temporary job in an insurance office provides unexpected clues in Bear's search for the truth. All the while the uncanny resonance of a school motto and a starring role in a staff pantomime occupy Bear's thoughts and energy as the mission unfolds.