Mugaldekoak is set in the early 40s, when, on this side of the border, the wounds of the Civil War were still open and, on the other, they were living under occupation by the German Army. The tale revolves around the Comète Network, an initiative developed during World War II on the border with Navarre: the clandestine evacuation of British pilots brought down in enemy territory.

The year 1914. The Lasarte racetrack announces a race with a never-before-seen prize for the winning horse. Eight of the best horses and mares in the world have registered. Fans and heavy betters from all the continents gather to participate in the great event: the Half Million Grand Prize.