The episode was written by Melinda Hsu Taylor and Rebecca Sonnenshine and directed by Jesse Warn.
Stefan is found and saved by Qetsiyah (Tessa in present time played by Janina Gavankar) who is later revealed that she is a powerful witch from Silas' past.
She managed to escape from the Other Side when Bonnie (Kat Graham) dropped the veil and now she tries to kill Silas by herself, but she needs Stefan for her plan.
In the meantime, Silas still looks for Katherine and Nadia (Olga Fonda) tries to convince him that she is on his side and wants to help him find her.
Elena distracts her so Katherine can escape but Nadia reaches her and leads her to her car where Silas waits for her.
Tessa wants to link Stefan to Silas to weaken his mind power because that is the only way to face him and kill him.
"[7] Stephanie Hall of KSiteTV gave a good review to the episode saying that "season five has been on a roll and "Original Sin" was no exception".
She was threatening and extensively powerful as a witch, while also believable and grounded in real human emotions.
"[2] TheDude35 from Bitch Stole My Remote said that it was a great episode and that "finally someone has explained the doppelgänger situation" and he loves when "questions get answered every once in a while".
[9] Christopher Monigle from Star Pulse didn't like the episode saying that it was "a convoluted mess" and that "[Original Sin] is another reason to worry about the quality of the show".
The writers failed to pull together the different parts of last year's central narrative together and far from resolving it this season.