House of Cards season 6 is finally here and with that, the knowledge of who killed Frank Underwood has been revealed. Kevin Spacey was fired by Netflix ahead of production on the final season, given the multiple accusations of sexual misconduct brought against him, leading to a significant rewrite that killed off his character entirely. That has been easily the biggest mystery heading into the final season and those who have seen it now know the answer.

Warning: massive spoilers ahead for House of Cards season 6. The events of season 5 already made it clear that Claire Underwood (Robin Wright) was going to get her chance in the power seat. But instead of having to navigate around her husband Frank Underwood, with whom she racked up an impressive resume of covered up misdoings and a body count, she's now moving on without him. But the death of her "beloved" Francis remains a mystery almost until the very end of this season and, ultimately, the series as a whole.

There are two parts to the character's death. The public narrative is that Frank Underwood died in bed next to Claire, who is playing the part of the grieving widow. Thanks to an autopsy, it was revealed that he died of an overdose on medication related to his liver transplant. Simple enough and believable enough. But that was what the public was told. The real story is far more in line with what people have come to expect from the show.

Related: First House of Cards Season 6 Trailer Ditches Kevin Spacey's Frank Underwood

The mystery is played up throughout the duration of the eight episodes. Did Claire do it? Did Bill Shepard (Greg Kinnear) and/or Annette Shephard (Diane Lane) do it? It's not until the final minutes of the last episode that we get the answer. Doug Stamper (Michael Kelly), easily the most loyal man to Frank since the very beginning of House of Cards, killed him.

As things are winding down, Claire and Doug meet in the Oval Office. She drags a confession of out him. What we learn is that Frank had intended to kill Claire. Doug's whole motive from the very start has been to protect Frank and his legacy. The man had already done a lot to tarnish his reputation and, in Doug's eyes, the only thing he could do was kill Frank in order to save him from himself. So, Doug used Frank's medication to kill him, leading everyone to believe it was an overdose.

The confrontation only intensifies after the confession. Claire tries to get Doug to agree that he's happy Frank is out of the picture. Doug responds by pulling out the letter opener gifted to him by Frank, holding it to Claire's throat. Eventually, Doug backs down. And then Claire, in turn, stabs him and suffocates him, just to make sure the job is done. Doug killed Frank, then Claire killed Doug, sort of tying up every single loose end.

And that's where we leave off. Claire standing in the Oval Office, pregnant with a child that may or may not be Frank's, Doug's dead body lying there. How she manages to resolve any of this is unclear, as that's where the season, and the series, concludes. House of Cards season 6 is on Netflix streaming now.