'For All Mankind' season 4 episode 6 review: Culmination of a storyline decades in the making

Close up of an older man speaking into a microphone at a big conference. He has short gray hair, beard, and moustache. He is wearing gold glasses and some black headphones. The man is dressed in a dark suit, white shirt, and red and blue striped tie. On his jacket lapel there is a small American flag pin. In the background you can see lots of well-dressed people sitting down, listening, as well as some official looking flags.

Multi-season arcs are now the standard in prestige T.V., but most shows' stories don't unfold over multiple decades. Four seasons in, "For All Mankind"'s alternative history of the space race now stretches from the late-1960s into the early 21st century, and seeds that were planted 30 (fictional) years ago are now coming to spectacular — and extremely satisfying — fruition.

The relationship between NASA boss turned defector Margo Madison (Wrenn Schmidt) and her protégée Aleida Rosales (Coral Peña) has been integral to the show since its early days. It went through a significant power shift in season 3 when Aleida suspected her boss might be caught up in some dodgy dealings with the Soviets. "Leningrad" picks up those threads and it's utterly captivating to watch.