Northern Ireland and the Isle of Man are almost unique in holding motorcycle races on (closed) public roads.
The film follows the racing careers of Joey Dunlop (1952–2000), who won five consecutive TT Formula One world titles and his brother Robert Dunlop (1960–2008), whose sons Michael (born 1988) and William (1985–2018) were successful road racers.
He was killed during a race in Tallinn, Estonia, when his bike left the track and crashed into a tree.
Robert Dunlop suffered multiple injuries after his rear wheel collapsed during the 1994 Formula One TT, but after two years' rehabilitation returned to racing in the Super Lightweight class on a bike specially modified to accommodate his damaged leg and wrist.
The film comes to a climax when Michael, a legitimate entry to the 250 cc race of that competition, but against the strong wishes of the organisers, forced his way onto the starting grid on 17 May 2008, two days after the death of his father and the day before the funeral, and won the race.