Rosa Lulli, has an illegitimate 20-year-old son, named Stefano, who lives with her in the house of Professor Arlotta. Stefano is in love with Lydia, the granddaughter of the professor. The couple has a gambling addiction: the need to obtain a large sum to meet gambling debts, which pushes him to accept the loving invitation of Jeannette, owner of a dance school, where Stefano goes to play.