The final episode of most mysteries series is all about the denouement, the murderer, the reveal. But not when it comes to The Beast Must Die. Everyone agrees the beast being dead is a good thing, for one. Justice for his death would not be arresting someone but thanking them. And as for who did it, well, that's been evident from the beginning.
Frances: I'm not the one you should feel sorry for. I've had so much love in my life.
By waiting to kill off George until the very end of the show's penultimate episode, the series was left with only one installment to solve the whodunit. George died at home, with all four family members present, making them the four most obvious suspects. The murder weapon was poison, tramadol, a pain killer. Poison is a woman's weapon, though one could imagine Phil using it as well since he's a child. (Also, the show has made it very clear he's to be regarded as not very masculine.) In fact, everyone who would like the beast to die would use it, so that doesn't narrow it down very much at all.
Perhaps the show could have zagged here, have Lena be the one to poison George for what he'd done to her, or Vi, for what he'd done to Lena, or even Marta, to free her mistresses. Phil's also an obvious suspect, so obvious the show goes so far as to go down to the station and confess halfway through the episode. (He didn't do it, obviously, though since the show left this stage until late, it felt close enough to time that it might have been the real deal.) Heck, even Joy could have done it, though she's the least likely since his death dethrones her rule over his home.
But the fact is, none of these people were likely to free themselves, trapped in the miserable cages they'd retreated to in the face of living with George. They may be free now and seeing Vi stand up and throw Joy out was a catharsis worthy of any finale. Also, her final scene with Lena as the two sisters reunited, free of the man who kept them divided, was lovely. But their escape was not of their making, just luck. But there's hope for the future, as the cops return Phil home, knowing full well his confession is false.
Phil's brave but misguided voluntary confession was trying to protect the women in his life in a way his father never would, but it wasn't going to work. No, Occams razor says that the most likely suspect is the one who did it, and to the show's credit, that's where they squarely lay the blame: Frances. She poisoned George on the boat that morning, drinking some herself so he would trust her, and then giving him the flask to slowly drink from for the rest of the day so that he would die hours later, far away from her. It was as close to a mystery doing the "Iocaine powder" solution as I've seen. it's also why poison is the weapon of those who cannot bring themselves to kill. It works slowly enough that there's time to wash your hands of it.
Frances admits to Strangeways she was initially planning on a boating accident, but once she was found out, it stopped being a rational plan she could pull off. But to be clear, I don't think that was ever really a solution. She had too many other opportunities before Strangeways knew her identity, and she couldn't bring herself to take them. Whatever she tells us, this was always the way. And perhaps, had Strangeways not been there, if the Isle of Wight cops were still social workers first and detectives only when pressed, she might have gotten away with it too.
But this solution isn't what matters, not really. Frances will not be arrested. She throws herself into the ocean, drowning her sorrows forever, while pushing Strangeways in as well, his life vest keeping him afloat. (Always wear a life vest while boating, kids, especially when sailing with a murderer. It will save your life.) But Frances' death is beside the point. The point is that George's death has allowed her well of grief to overflow, the dam to break. Her child is gone, her life is over, but at least she's had her revenge before she went.
And now we are left with Strangeways, a protagonist left behind to carry the show. Season 2 has already been greenlit, with writer Gaby Chiappe coming up with a new original story. Whether or not the remaining vestiges of the Rattery family will be involved remains to be seen, but chances are the story will move on, along with the actors. It also seems unlikely, barring another pair of high profile castings like Jared Harris and Cush Jumbo, that a season two could hit the same highs that this one did. But The Beast Must Die's first season was full of surprises, so perhaps we should not count Strangeways out yet.
All episodes of The Beast Must Die Season 1 are now streaming on AMC+.