At the story's end, Kit and Nathaniel are reunited. Although the story ends before they are actually wed, there is no doubt that their marriage is imminent.
Nat had asked Kit to go with him before, but Kit had demurred, and, as far as he knew when he saw her last, she was going to marry William Ashby. Realizing that they were not right for each other, however, Kit had broken off her engagement with William, who ended up marrying Kit's cousin Judith, a much better match for him, instead. After surviving the typhoid epidemic and being accused of witchcraft, Kit had come to accept that she would never be at home in Connceticut Colony, and "all her plans now turned toward Barbados", and Nat, whom she finally perceives as being the one who has loved her all along, just as she is.
When Nathaniel arrives and learns that Kit has not married Ashby, he knows from Kit's demeanor that she will accept his own proposal this time. Being a proper gentleman who wants to do things right, Nathaniel resolves immediately to ask her Uncle for her hand. Kit wants to see the new boat Nat has managed to acquire, but Nat refuses. He wants her to wait until they are married; when he takes her aboard, "it's going to be for keeps". The book ends with the two of them walking to the Woods's residence, to get the approval of the family and make their plans official (Chapter 21).