The Smoke Eaters.

A society couple lose their two-year old son in ship-fire and a fireman, finding the child, adopts him. The society couple adopt a baby girl. Both children grow up and meet in later years but the girl has an affair with a rich profligate. Meanwhile, the boy has become a fireman and through his instrumentality the girl is saved from death in fire. She gives up the rich youth and marries the firefighter.