...Season 1 Episode 6

https://screenrant.com/dexter-original-sin-deb-lumberjack-ending-foreshadow-explainer/

A scene between teenage Deb and Dexter Morgan in Original Sin (https://screenrant.com/db/tv-show/dexter-original-sin/) season 1, episode 6 features a line that teases Dexter's divisive season 8 finale fate.