Watch Supernatural executive producer Jeremy Carver preview this week’s episode, “As Time Goes By,” which features the Winchesters’ paternal grandfather, below.

“One of the great unknowns in our Winchester family mythology is explored this week when the boys discover and explore the side of the family that they never knew, specifically their father’s side of the family, the Winchesters,” Carver previews.

“This episode basically involves time travel and the reunion of sorts of Sam and Dean and the grandfather they never knew, whose name is Henry Winchester,” played by Gil McKinney.

“Through their grandfather, they learn not just more about the relationship — the very specific relationship — that John had with his father that, of course, affected them as John’s sons, but the quote unquote family business, as it were, that Henry was involved in that for them and for Supernatural fans, I think, will really complete the loop in terms of this Winchester family mythology,” Carver concludes.

We learned in season 4 that the boys’ mother, Mary Campbell, also came from a long line of hunters, though she left the family business to raise her family. Sam even hunted with his maternal grandfather, Samuel, during the year between seasons 5 and 6 when he was without his soul.

As far as we know, John was unaware of the supernatural until Mary’s death, so we’re curious to see how the backstory with Henry plays out!

“As Time Goes By” airs Wednesday, January 30 at 9:00 p.m. ET.