7 Theories We Have After the 'This Is Us' Season 4 Fall Finale (PHOTOS)

Meaghan Darwish

[Warning: The below contains MAJOR spoilers for Season 4, Episode 9 of This Is Us, "So Long, Marianne."]

The This Is Us Season 4 fall finale left fans with yet another cliffhanger as, ahead of the midseason break, the show flashed forward nine months.

The main causes for viewer concern have to be Rebecca's (Mandy Moore) deteriorating mental health and Randall's (Sterling K. Brown) apparent estrangement from siblings Kate (Chrissy Metz) and Kevin (Justin Hartley). Plus, Kevin's already engaged and expecting a baby with his mysterious fiancée?! Needless to say, there's plenty to theorize about in the meantime.

'This Is Us': Chrissy Metz & Chris Sullivan on What's Next for Kate and Toby

'This Is Us': Chrissy Metz & Chris Sullivan on What's Next for Kate and Toby

Will another man come between the new parents? And what's the deal with that mysterious Marc-Kate relationship?

Click through the gallery above to see a few of our theories and don't miss This Is Us when it returns in January on NBC.

This Is Us, Season 4 Return, Tuesday, January 14, 9/8c, NBC