An intrepid band of resistance fighters battle for Spanish independence in 1810. In order to achieve their objective, they must first haul a six-ton cannon across the wide expanse of Spain's mountains. During their perilous journey, a dramatic love triangle emerges between a dashing resistance fighter (Frank Sinatra), his sultry mistress (Sophia Loren), and a British Navy captain (Cary Grant) recruited for the cause.
In 1810 Spain, citizens band together to fight Napoleon's troops after the Spanish army has retreated. Along with other resistance fighters, Miguel and his mistress Juana are trying to move a huge cannon to the walled city of Avila. Capt. Anthony Trumbull of the British Navy is sent to assist them, and it isn't long before Capt. Trumbull falls for Juana. A clash of cultures and the romantic triangle create tension between the heros who are fighting for the same cause.