Filming of this show takes place in Atlanta, Georgia. Another show that's been filmed there is Constantine (2014). Joseph Morgan (Klaus Michaelson) is best friends with the lead actor of the show, Matt Ryan.
When Elijah calls Rebekah in her first present day scene of the show, she is sitting in a bathtub holding a white Samsung Galaxy phone, presumably the s4. While out of focus, the top of the phone is visibly upside down, the speaker and front-facing camera shown where the Oval home button should be. She is effectively talking into nothing, although since both vampires possess superhuman hearing abilities, neither one might have noticed the difference in sound quality.
Claire Holt (Rebekah) and Phoebe Tonkin (Hayley) previously starred together in H2O: Just Add Water (2006).
A body double portrayed Esther because the actress who portrays her, Alice Evans, was pregnant at that time so they had to replace her.
Title meaning: a reference to the vow Klaus, Elijah and Rebekah swore after their mother's death. It is also a reference to Elijah's point of view in this episode, and to the fact that he has always taken the vow to heart more than the others.