The Campbells - Season 1 Episode 10 Vendetta*

Captain Sims is challenged to a duel in response to events in his military career. James must mediate to prevent bloodshed. After recieving the challenge, Sims sends Harriet and Rebecca to stay with James where they will be safe. He sends Rebecca along with a box for safekeeping but makes her promise not to open it. Harriet is unaware what is going on and asks James to investigate. James finds out about the duel and he and Harriet reason with Rebecca to reveal what's in the box. James finds Sims' war journal which explains the events leading to the duel. He must then arrive in time to prevent the duel and save Sims.