Who is Capt. Thomsen from Effi Briest and what is their importance?

Unseen in the novel, Thomsen is a veteran of the lucrative "China run," who settles in Kessin at the dapper age of 60, sells his old ship and buys what becomes Geert von Innstetten's house. The crocodile, shark and ship are Thomsen's. He is accompanied by 20-year-old Nina, either his granddaughter or his niece and by an unnamed Chinaman, who at first serves as his servant but later becomes more of a friend. Nina marries another sea captain and suddenly disappears. The Chinaman dies two weeks later. Thomsen arranges a plot and an inscribed stone outside the Christian cemetery. Frau Kruse confirms to Effi that the Chinaman is in love with Nina.