At the end of the episode, while Eleanor sits at her bar before Gates brings Silver to her, the "Skye Boat Song" can be heard being played on the violin in the background. This anachronistic piece details the flight of Prince Charles Edward Stuart to the Isle of Skye after his defeat at the Battle of Culloden. The piece is also the theme song for another Starz television show scored by Bear McCreary- Outlander. The version of this song that is possibly the most famous was composed by Robert Louis Stevenson- author of Treasure Island.
Captain Rakham tells Charles Vane that the people in the opium dens thought themselves too good to wear a condom. The condom had not been invented yet, in the 1600's. The condom was not invented until 1855, and not commonly used until the early 1900's. EDIT: Although rubber condoms were not invented until the 19th Century, there have been various forms of sheaths used since ancient times, often animal intestines or bladders. The first recorded use of "condom" (various spellings) was in 1706, thus the use of the word in 1715 is possible.
There is 1 unnamed character death in this episode making the season count 47.