How did Bessie begin to share Hagberd’s insanity regarding his son?

When that stranger asked Bessie about what’s the matter why this old man is behaving like an insane person then with a flow in the conversation Bessie started sharing that stranger that the reason of insanity of Captain Hagberd is his son. He lost his son somewhere in sea as he always used to say and he was for his son for a long time. He keeps on roaming here and there in search of his son.