Marta, a child orphan of a miner, has a great friend, Nicola, her age, with whom she spends hours of games, made of fantastic journeys inside the mine. But the difficulties of the owners closed the mine and the miners were forced to look for work elsewhere. So Marta and Nicola are forced to separate. Years pass and the old mine is reopened and both Nicola, now a man and Marta, who has become an elementary teacher, return to the place, their new meeting arouses in two different emotions: Nicola falls in love with his old friend, but is not reciprocated because Marta gets engaged with an engineer, Carlo.