A tenacious female British secret service agent is assigned to a liner carrying medical supplies during the First World War, to protect it from German saboteurs. On board, she becomes distracted by an unforeseen romance, but the hardening realisation that the enemy may have infiltrated the ship sharpens her focus once again, and she pulls out all the stops to unmask the suspected spy. Drama, with Amanda Ryan, Edward Atterton and Jacqueline Bisset