Why do Dangerfield and Marion fight when she returns home from her trip?

Dangerfield awakens to his furious wife's return. He's forgotten to pick her up at the train station. The house is a wreck, and Dangerfield's obviously been drunk. When Dangerfield insults Marion's father, she slaps him on the face, and the baby begins to cry. Hung over, Dangerfield threatens to kill the baby if it isn't quiet. He leaves his wife in tears and goes into Dublin, thinking she doesn't have the guts to divorce him.