Thomas Maggs, the crippled son of the village publican, lives with his family on the Suffolk coast. His life is shaped by the seasons: fishing, farming and summer visitors, but all that Thomas longs for is adventure and a chance to go to sea. One day a mysterious artist arrives and immediately becomes a source of fascination to Thomas. His name is Charles Rennie Macintosh, or Mac, as the locals call him. Yet just as their unlikely friendship begins to bloom, war with Germany is declared. As the summer guests flee, they are replaced by regiments of soldiers on their way to Belgium and the community becomes gradually more suspicious of the artist and his increasingly eccentric behaviour...