Watch a sneak peek of the episode featuring Simon's quest to remove the Mark of Cain:

The title (Season 3, Episode 12) refers to the 12th episode of the third season of Shadowhunters , which originally aired on March 4, 2019 . Where to Watch "Original Sin"

The full episode can be streamed on the following official platforms: : Available for streaming with a subscription. Disney+ : The complete series is available on Disney+ .

: Episodes are often available on the Freeform website or app with a TV provider login.