Set in St. Andrews, Scotland during the hidebound Victorian era, the story opens in 1866 as 15-year-old Tommy Morris (Jack Lowden) heads to the links with his father, Tom Morris (Peter Mullan). Already a legend, "Old Tom" is greens-keeper for the Royal & Ancient golf club, where he established the standard of 18 holes per round; as well as the town's club- and ball-maker; and thrice winner of the first major golf tournament, the Open Championship - which he founded in 1860.

Tom Morris has secured his place in the history of the ancient game. But Tommy will soon outshine him, retiring the Open's prize Championship Belt while still in his teens (by winning it three times in a row), and, as the "dashing young man of golf," drawing flocks of spectators to the sport and becoming its first touring pro.

Despite their shared passion, father and son repeatedly clash over the unwritten rules of social class, culminating in Tommy's marriage to a woman of lower standing with a shameful secret in her past. Tommy's beloved wife Meg (Ophelia Lovibond) figures in this true story's climax, as Tom makes a fatal isjudgement that strips Tommy of everything he holds dear. From the ashes of that fateful choice, Old Tom rises to a mission that carries him through the final decades of his life: Honouring Tommy.