Complex sentence: Darrow is alone on his ship "Heron" where he reminiscences about his childhood where he was the son of a captain and was nicknamed "Mouse" by the family like crew.
Split into simpler sentences: Darrow is alone on his boat "Heron", where he reminiscences about his childhood. It is revealed that he was the son of a sea-captain and was nicknamed "Mouse" by the family-like crew.