I do controversial things like spell the name Cass, instead of Cas. When it comes to invasion movies, I almost always root for the aliens.

TNT frequently hosts Supernatural marathons and sometimes they do so in such a brilliant way: by picking common themes within episodes. I happen to be one of those people who, when not plugged into earbuds listening to podcasts or music, allows television to fill the silence as background noise. Not so long ago, TNT broadcasted all the Supernatural episodes in which time travel was an element of the plot, and I enjoyed listening to the dialogue while puttering around the house.

If you watch the show, then you know the “daddy issues” trope that is the cornerstone of the series: the father (God/John) that one son (Michael/Dean) worships and the other son (Lucifer/Sam) rebels against. Then one day, the father figure is no longer present and the sons try to figure out who they are in his absence. It’s a dynamic that intrinsically pits son against son, but doesn’t pigeonhole one as good and the other evil. Instead, it’s obedience versus defiance and fate versus free-will.

In The Song Remains the Same (season 5, episode 13), Sam and Dean are whisked away to 1978 to stop the angel Anna from killing their mother and preventing their births. There are funny and interesting things that happen in this episode, including Sam being super creepy with his mom. But what stopped me in my tracks and had me hitting rewind was the dialogue between Dean and the archangel Michael. Now, for those not familiar with the series, angels need a “vessel” in order to physically manifest on Earth, which is a willing human, but it can’t be just any ol’ person. Angels are paired up with human bloodlines whom they can possess, and the archangel Michael wants himself a Dean-suit in a bad way, so that he can fulfill his destiny by going toe-to-toe with his brother Lucifer.

DEAN

How’d you get in my dad, anyway?

MICHAEL

I told him I could save his wife, and he said yes.

DEAN

I guess they oversold me being your one and only vessel.

MICHAEL

You’re my true vessel but not my only one.

DEAN

What is that supposed to mean?

MICHAEL

It’s a bloodline.

DEAN

A bloodline?

MICHAEL

Stretching back to Cain and Abel. It’s in your blood, your father’s blood, your family’s blood.

Holy shit, Batman! I went into full on giddy fan girl mode. At the time of the original airing of the episode, I gave no thought to the implications of this dialogue, but now? That little seed planted in season 5 is the goddamn premise of season 9 and 10! Dean has the Mark of Cain. Dean and Sam are the descendants of Cain; two of his many “poisoned issue.” They are legion. While watching The Executioner’s Song (season 10, episode 14), I nearly squealed with excitement every time Cain called Dean “son,” and I don’t think I would have been as delighted with this episode had I not been reminded that Cain and Abel were the original vessels of Michael and Lucifer.

Here we are in season 10, and Dean is faced with the possibility of having to kill his brother again. Now, I adamantly believe that this is not laziness on the part of the writers or that they’re running out of ideas, but rather, they are staying true to the show’s most prominent and important motif: is free-will an illusion, and is fate inescapable? A concept tested in The Monster at the End of the Book (season 4, episode 18), in which the brothers constantly tried to derail prophesied events, only to find kismet steering them back on the divine course.

The show will inevitably revisit these questions about fate and free-will; in fact, they have to. In a universe where magic exists, prophecies are foretold, and God is on a permanent vacation, are humans simply the obedient meat puppets of the divine or potential wrenches in the wheel of the divine plan? They’ll likely resolve these questions whenever the series ends, and I’m a little nervous to find out the answer.