One of the best aspects of Marvel's Agents of S.H.I.E.L.D. is that the series is structured much like the comic books it's based on. Each season follows an "event" storyline that builds up into the ones that follow. The result is a series that brings the fans back season after season to see what's going to happen next, which popular characters from the comics will make an appearance, and how closely the series relates to the books.
Marvel's Agents of S.H.I.E.L.D.'s story arcs are called pods, and most seasons have one large one while others have two to three. Pods have been described as "7-10 episodes [that feature] little 'enclosed plotlines' that formed a larger whole." This structure will continue as the show enters its sixth and seventh seasons. Each pod has its fans, but some are considered significantly better than others.
Agents of HYDRA
What Happens: "Agents of HYDRA" is the third and final pod from the fourth season. With the main characters stuck in Aida's framework, life looks rather different. S.H.I.E.L.D. has fallen while HYDRA has taken its place, and the woman in charge is none other than Aida, otherwise known as Lady Hydra within the Framework. At her side is Fitz, whose father is still around to lead him down a path of darkness as Aida's righthand man.
Coolest/Most Bad-Ass Moment: When the team finally escapes in a massive fight at the very end.
What It Sets Up: The inevitable confrontation with Aida in the real world. However, things aren't as simple as they used to be thanks to the Darkhold...Was this a great arc?
The Hunt For Aida
What Happens: In the final two episodes of the fourth season, the team must find and deal with Aida, but there's a catch. She has found a way to make herself an Inhuman body in the real world, filled with the various powers she took from others within the Framework. As a result, catching and stopping her isn't as easy as it was previously. This arc also sees the end of the Framework.
Coolest/Most Bad-Ass Moment: When the Framework comes to an end for Radcliffe and he utters the line, "This is the way the world ends. Not with a bang, but a..."
What It Sets Up: The end of the fourth season establishes the events that build into "Lost in Space."Was this a great arc?
What Happens: In order to line up Marvel's Agents of S.H.I.E.L.D. with the rest of the MCU, "Uprising" is used to parallel the events of Captain America: The Winter Soldier. In that film, S.H.I.E.L.D. falls as HYDRA takes over, and "Uprising" shows the fallout of the destruction of S.H.I.E.L.D. from the perspective of the very agents of the organization that the series is based on.
Coolest/Most Bad-Ass Moment: Everything comes to a head when the Clairvoyant turns out to be none other than John Garrett, proving a traitor was among the agents all along.
What It Sets Up: "Uprising" doesn't directly set up another pod, but it does establish that the entire world has changed for Coulson and his agents. What will they do now that they have no backup, nobody to turn to, and the world out to get them?Was this a great arc?
What Happens: "Fallen Agent" closes out the third season with the prophesied passing of one of the primary Agents of S.H.I.E.L.D. The group must take on Hive as the master plan is finally revealed to threaten all humans and Inhumans on the planet - but who will live and who will perish?
Coolest/Most Bad-Ass Moment: When Lash makes his way into Hive's lair to free Daisy and perishes in the fight. It's a brutal scene with ramifications extending well beyond the episode for Daisy and the rest of the characters.
What It Sets Up: With Hive finally out of the way, Daisy leaves S.H.I.E.L.D. and becomes the vigilante Quake. That new identity remains for the rest of the series into Season 5. With "Fallen Agent" over and done with, it's time to introduce some new blood with "Ghost Rider" in Season 4.Was this a great arc?