An Italian fisherman's extended family is disrupted by the arrival of his widowed sister-in-law.

Carlo Roma, an Italian fisherman from San Francisco, is head of a happy family composed of his adopted son Tony, his helper Beppo, their housekeeper Angelina, and their pet seal Julius. The family's domestic bliss is disrupted when Carlo's widowed sister-in-law Stella arrives with her spoiled young son Rudolph. Stella ensnares the financially successful Carlo, and then begins alienating his family one by one. Her first victim is Julius, whom she banishes from the house. Next, she offends the affable Beppo, making him feel unwelcome in Carlo's house. Then after deciding that Carlo is not making enough money from his three boats, Stella suggests that he demote his three helpers, Beppo, Luigi and Pietro, from equal partners to paid workers, and as a result, the three leave Carlo to work on their own. Angelina is the next to go when she quits and marries Beppo. Tony is the last victim when Rudolph cruelly informs him that he is illegitimate and that Carlo is not his father. Devastated by the news, Tony runs from the house after Carlo harshly reprimands him. While on the run, Tony visits Beppo, who tells Carlo of Rudolph's cruelty. Together, Beppo and Carlo sail after Tony, who has taken Carlo's boat, and after catching up to the boy, Carlo denounces the interlopers and begs Tony to return. As Stella and Rudolph set sail for Seattle, the Roma family is happily reunited.