People have given this episode a poor rating purely because of what happens at the end of the episode. Yes, it happened, and it's not going to change. Why?
Dan Stevens did not sign on for a fourth season. The best thing to do was kill off his character, rather than alienating him from the family and making a horrible, painful mess out of his relationship with Mary. He was killed when they were perfectly happy with one another. Would it make sense to suddenly, on Season 4, Episode 1 write in that the character up and left his wife and newborn child, never to be seen again? That's what happens when the actor abandons the role; you get a killed off character.
Now, the remainder of the episode was supreme. The hunt, Shrimpy's estate and the picnic--all of these things were wonderfully executed, and truly built onto (or added a note of temporary finality) to the respective storylines, such as the Anna/Bates sub-plot. Everyone knows that this show is not a single plot, but many smaller ones built on top of each other to create an amazing drama. Disappointed as I am with Dan Stevens' decision, I won't give this episode an unfair review or rating just because I hate how it ended.
Season 4 is going to be a very interesting, very emotional experience and I'm looking forward to it.