The season-long saga of "who's in the grave?" has turned out to be kind of a masterstroke from the writers of Arrow. As mysteries go, it's proving to be a lot more involving than "who actually is Zoom?", probably because the stakes are higher. Whoever it is six feet under, the impact of the reveal will be felt by Oliver or somebody close to him.
There's not exactly been a drought of theories so far, mostly involving Felicity, but I've been toying with a few more possibilities, all of which will almost certainly be wildly wrong (but do actually make at least a little bit of sense). Cast your eye over them and then let me know what you think the possibility of any of these scenarios playing out on screen is when season 4 returns this month.
1. Captain Lance's sudden likability factor
On the one hand, Captain Lance being the body in the grave would feel like a real tragedy. Prior to season 4, Laurel's father and Oliver have always struggled to find a common ground, the Captain's opinion of the vigilante not an awful lot higher than of the terrorists who prowl the shadowy streets of Star City.
This season has seen that dynamic altered to something that would have been almost unthinkable way back in season one: there's an undercurrent of mutual respect between the two men. You may also have noticed a marked increase in screentime for Lance. The writers are practically working overtime to make him likeable.
If Quentin had been killed in season 3, the audience probably would have been all ¯ \ _ (ツ) _ / ¯ and felt a little sympathy for Laurel, but if it happened now, or in four months, I'd put money on most of us feeling a little more stirred.
2. Felicity and the mini Oliver equation
Cast your minds back to the opening scenes of the season 4 premiere. Vaguely surreal, wasn't it, seeing Oliver in apparent domestic bliss with (a somewhat reluctant) Felicity?
One exchange of dialogue from the scene in which the neighbours come to dinner sticks out in the mind. The female neighbour makes a point of encouraging Oliver and Felicity to get themselves on the waiting list for the best local school, even though they don't actually have a kid... yet.
Fast-forward to episode 10: in the teaser we see Thea call Oliver with the news that Felicity is in some kind of critical state. There's been a whole ton of speculation about Felicity surviving but being stuck in a wheelchair, in turn feeding Oracle whispers. But what if the wound from the gunshot leaves Felicity unable to birth a child?
When the mother of Oliver's son is killed - that's her in the grave, BTW - he's left to look after his offspring, and a heartbroken Felicity instead dives headfirst into her Oracle transformation.
3. Why can't Barry use time travel?
Regardless of who Oliver is mourning in the flash-forward, one burning question remains unanswered: why doesn't Barry merely use his ability to out-run time to travel back and alter the course of history in his present timeline?
Clearly the repercussions of playing with time can be dangerous, but if the person in the grave means anything to Oliver, chances are Barry could be convinced easily enough.
So what's the theory? Whoever it is (and this works best if it's Captain Lance) under all that dirt died saving Star City, a deliberate act of sacrifice, in the wake of which Damien Darhk fled. By going back to save Lance, Barry would undo everything he died for, and Star City thrown back into terror and chaos.
Arrow returns with season 4 episode 10, "Blood Debts", on January 20th, although we all know there'll be a whole ton more questions asked before we start getting any answers - and personally speaking, I'm beyond stoked.