After the Soviet Union invaded Finland in 1939, thousands of Swedes joined the fight alongside Finnish soldiers against an overwhelming enemy. In northern Finland, the Swedish F-19 squadron took part in the fighting. For many pilots, the battle was fatal.

An F-19 squadron of Swedish volunteers successfully defends northern Finland against an overwhelming Soviet attack. The risks are high, with two pilots taken prisoner by the Soviet Union. They are made an offer they cannot refuse.

The Winter War ends with the 1940 peace treaty, but the world war continues. In Stockholm, the role of two pilots who volunteered to fight for Finland as possible double spies is investigated.