Credit: ITV

MAJOR SPOILERS AHEAD! Stop reading if you don’t want details on the Downton Abbey episode that will air January 27 on PBS.

Are you ready for an edge-of-your-seat episode of Downton Abbey Season 3? As IndieWire previewed tonight's Episode 4: "If there is one episode of Downton Abbey you won’t want to miss, it’s this week’s. I won’t give anything away, except to say that the video preview ... doesn’t begin to prepare you for the high drama of the most tension-filled episode so far — in fact, until the season finale."

What's the big deal? Well, after tonight's ep we're going to be minus one Crawley sister … but plus a new baby! 

All of Season 3 has already aired in the UK, and — according to Heroes and Heartbreaker's play-by-play recap — Lady Sybil goes into labor, but there are complications and a fight between her doctors (Dr. Clarkson and Sir Philip) on what to do pits family members against each other.

At some point it seems like things are going to be fine, because Sybil gives birth to a baby girl! However, to quote the H&H recap:

"Sybil’s very tired, but right before she falls asleep, she asks Cora to make sure Tom doesn’t move to Liverpool. She wants to make sure Cora’s on her side when she has to confront Lord G. about not allowing the move 'backwards.' [However] Sybil wakes up in pain and starts having a seizure a few hours later. The entire family’s in her room (along with the two doctors) trying to calm her down, but it’s not working. All of a sudden, the arrogant Sir Philip is not so sure of himself any more. Clarkson tells Lord G. that nothing can be done once the seizures have started. Everyone is just frantically trying to do something—anything—to help, but it’s a hopeless situation. Sybil’s thrashings slow down, but she can’t breathe, and as the family watches horrified … she dies."

Wow. So expect huge tensions in the family after this, with Cora (who had backed Dr. Clarkson's diagnosis) blaming Lord Grantham (who backed Sir Philip) for his role in Sybil's death. And poor Branson: Now he's stuck with this crazy family. But, really, poor Sybil! She was the kindest and bravest of them all.

Sources: IndieWireHeroes and Heartbreakers