In 1947, Visconti went to Sicily with a small amount of capital advanced by the Communist Party, to make a film that expanded into a mammoth epic on the conditions of the poor workers and peasants of the South, and their struggle to liberate themselves from oppression. Planned as three episodes, eventually only the one was finished that bears the title, La Terra Trema.

The Valastro are a representative family of fishermen. Their enemy is not the sea, against which they pit themselves in the miserable struggle for survival, but the exploitation by other men, that forces them to undertake the struggle in the first place. Without the capital to own or equip the boats they go out in, or the organisation to market the meagre haul of fish they bring in each morning, they are utterly dependent on the wholesalers who own the boats and pay the fishermen a pittance for their catch. The Valastro mortgage their house and attempt to set up an independent business with the proceeds, but the need to recoup their initial financial outlay forces them to go out to sea at all times and in all weathers. One night they are caught in a storm — their boat is destroyed and with it their entire livelihood. The mortage is foreclosed and the Valastro are left with nothing, except the possibility of working on other families' boats.

The story of the family is centred on young 'Ntoni, who comes to assume the position of the father. He leads a spontaneous revolt of the fishermen against their oppressors and is carted off to jail. In the final scene, though the Valastro have been utterly destroyed, "Ntoni takes hope In the future, realising the need for collective, rather than individual, action.