Depending on which series you are following, here are "solid" post-episode discussion summaries or focal points for some of the most popular shows with this episode designation:
An anthology-style episode within an episode, it features a traveler visiting a remote museum filled with artifacts from past technology-driven tragedies. [S4E6] Episode #4.6
A rare moment of character growth where Emily stands up for herself after Gabriel abandons her on a ski slope to chase after an expert skier. Depending on which series you are following, here
Often cited as one of the best finales, fans love to hunt for "Easter eggs" that link the various Black Mirror stories together, such as the references to the Ouroboros. You: "Best of Friends " (S4E6) [S4E6] Episode #4.6