In 1943, after their successful mission in Navarone, Mallory (Robert Shaw) and Miller (Edward Fox) are sent to find and kill "Nicolai". Originally thought to be a traitor who informed the Germans about Miller and Mallory during the Navarone mission, Nicolai is now known to be a dedicated German spy, and is believed to be disguised among the Yugoslav Partisans as a Captain Lescovar (Franco Nero).To get to Yugoslavia the two men pair with "Force 10", an American sabotage unit led by Lt. Col. Barnsby (Harrison Ford) and having with its own mission in Yugoslavia. To maximize security, Force 10 steals a plane from Termoli rather than requisitioning one, but are spotted by US M.Ps before takeoff. Weaver (Carl Weathers), a US Army sergeant under arrest by the MP's, joins with Force 10 and forces his way onto the plane. Barnsby and crew successfully "escape" Termoli only to be shot down by German night fighters over Yugoslavia. Only Barnsby, Mallory, Miller, Weaver and Reynolds (Angus MacInnes) manage to escape the crippled plane.
Mallory and Miller are back. The survivors of Navarone are sent on a mission along with a unit called Force 10, which is led by Colonel Barnsby. But Force 10 has a mission of their own which the boys know nothing about.
