There's been no shortage of villains on this season of Agents of S.H.I.E.L.D. We've had superpowered villains stop by for an episode, we've had the "real" S.H.I.E.L.D. offer some semi-villainous presence, and this week's episode proves the Inhuman camp has a few nasty characters hidden within.

But no one's been more villainous than Skye's dad, Calvin Zabo (Kyle MacLachlan). Cal's been the closest thing Agents of S.H.I.E.L.D. has had all season. But there's one aspect of his character we've yet to see- his monstrous transformation into Mister Hyde!

In Marvel Comics, Calvin Zabo is only half the character. There's the Cal we know, and the version of him that comes out when he injests a special serum- transforming him into a massive creature with strength like the Hulk. Agents of S.H.I.E.L.D. hasn't shied away from Cal using super-strength, but it's never outright said that he also transforms into a horrifying monster creature.

Until now, anyway. The latest promo art for the season finale, S.O.S., seems to hint we'll actually be seeing Cal in the season's final episode. The artwork shows Fitz and Simmons brandishing guns and taking on an unknown character who's only visible via an arm. The text on the pic tells us all we need to know.

"Can Fitz-Simmons face what Hydes in the shadows?"

"Call this science? Call this mad!"

Kind of obvious, isn't it. Hyde's coming! Although it might still a tease. For all we know, this is ABC's way of slyly hinting at the character's comic book alter ego without actually saying straight-up that Hyde is coming. Maybe S.O.S. will end with Fitz and Simmons facing off with regular old Zabo. However, a detail at the end of the most recent episode- Cal holding a couple of vials of serum, which he's clearly just drank- implies he might actually be seconds away from a monstrous transformation. Fingers crossed.

Agents of S.H.I.E.L.D.'s finale will air this Tuesday at 8:00 PM.