Engineer Mario Camargo, originally from Argentina, arrives in Cuba to work on the construction of a new industrial complex. He came from France, where he had lived most of his life. Mario had never thought about what homeland meant to him. He had always lived wherever he felt comfortable. In Cuba, Mario meets architect Marta Alea, a passionate patriot who devotes all her energy and abilities to building a new life. Seeing the enthusiasm of Marta and her friends, their devotion to the ideas of the revolution, Mario realizes that in our days, when the face of the world is changing, one cannot be a man without a homeland.