Gringalet was based on a stage play by Paul Vanderberghe, who also essays the title role in the film version. Charles Vanel stars as a powerful industrialist who learns that he has a grown, illegitimate son named Gringalet (Vanderberghe). Once he's over the initial shock, the industrialist insists upon introducing Gringalet to his outraged family. They treat the boy with barely concealed hatred until he finally wins them over. Also repeating her role from the stage version of Gringalet is Marguerite Deval as the imperious family matriarch.
Source : allmovie.com