Thomas Maggs, the son of the local publican, lives with his parents and sister in a village on the Suffolk coast in 1914.
He is the youngest child, and the only son surviving. Life is quiet - shaped by the seasons, fishing and farming and the summer visitors. Then one day a mysterious Scotsman arrives. To Thomas he looks for all the world like a detective, in his black cape and hat of felted wool, and the way he puffs on his pipe as if he's Sherlock Holmes.
Mac is what the locals call him when they whisper about him in the inn. And whisper they do, for he sets off on his walks at unlikely hours, and stops to examine the humblest flowers.
He is seen on the beach, staring out across the waves as if he's searching for clues.
But Mac isn't a detective, he's the architect Charles Rennie Mackintosh, and together with his red-haired artist wife, they soon become a source of fascination and wonder to Thomas. Yet just as Thomas and Mac's friendship begins to blossom, war with Germany is declared.
The summer guests flee and are replaced by regiments of soldiers on their way to Belgium, and as the brutality of war weighs increasingly heavily on this coastal community, they become more suspicious of Mac and his curious behaviour... In this tender and compelling story of an unlikely friendship, Esther Freud paints a vivid portrait of a home front community during the First World War, and of a man who was one of the most brilliant and misunderstood artists of his generation.