Each episode told a portion of the overall story, from the response to the disaster in episode one, focusing mainly on the firefighters and the scientists and engineers working at the plant who were the first to respond to the disaster and tried to contain it. Episodes 2-4 were all about trying to contain and mitigate the results of the disaster. The series does a great job of showing not only how bad it was but how bad it could have been had steps not been taken to prevent a second explosion, which would have killed millions and contaminated most of Europe with radiation fallout. The final episode focused on the trial of those who ran the plant and laid out in great layman's terms exactly why the reactor core exploded.
The acting and writing of the series were top-notch. It accurately told the story yet kept the details understandable. I actually researched the disaster for a class in my engineering program, and I was impressed that while some aspects were embellished and dramatized for TV, they got all the important stuff correct, including how the plant was not maintained correctly and how the cheap materials played a pivotal role in what happened.
The Blu-Ray set is a two-disc set. The A/V quality is excellent, as the show looks and sounds great in the format. The extras include short inside-the-episode segments for each episode, then a handful of behind-the-scenes and making-of clips that run anywhere from a minute and a half to about 10 minutes. It's not a ton, but it's good for what is there. It is a pricey set for a two-disc, five-episode series, but it is worth it for those who want to support the physical media and keep it around as long as possible.