"Mr Standfast" is a thrilling espionage novel set during World War I. The protagonist is a British intelligence officer who is tasked with tracking down a German spy. The mission takes him on a dangerous journey across war-torn Europe, where he encounters a variety of characters and faces numerous challenges. Along the way, he uncovers a plot that could change the course of the war. The novel is a blend of suspense, action, and romance, with a strong emphasis on patriotism and duty.