[This is a review of Agents of S.H.I.E.L.D. season 4, episode 21. There will be SPOILERS.]

This season, Agents of S.H.I.E.L.D. has featured three distinct storylines each following different arcs, first introducing Robbie Reyes, aka Ghost Rider (Gabriel Luna), then shifting focus to Dr. Holden Radcliffe's Life-Model Decoys, particularly Aida. The latest storyline in Agents of S.H.I.E.L.D. season 4 has featured the agents trapped inside a virtual reality that depicts an alternative history based on certain tweaks Aida made to the timeline. The Framework storyline allowed Agents of S.H.I.E.L.D. to bring back fan-favorite characters like Grant Ward (Brett Dalton) and Antoine Triplett (B.J. Britt) as well as display incredibly different sides to the show's main characters.

However, with Aida's endgame being revealed through the mysterious Project Looking Glass, the agents were forced to exit the Framework in last week's episode, 'Farewell, Cruel World!' before the LMD could build herself a human body and gain the ability of free will. Although most of the agents were able to leave the Framework through Radcliffe's back door, Mack decided to stay and be with the simulated version of his daughter Hope (in reality, Hope died soon after she had been born). Now, the agents may have left the Framework behind, but there's still plenty of obstacles to be faced in the real world.

In this week's episode, 'The Return' -- written by showrunners Maurissa Tancharoen and Jed Whedon and directed by Kevin Tancharoen - the agents reunite after exiting the Framework. However, they face an even deadlier enemy in Anton Ivanov, who's received some improvements since they last fought him thanks to Aida's technological tampering. Meanwhile, Aida/Ophelia continues to acclimate to experiencing reality in a human body.

The Agents Return

Phil Coulson in Agents of SHIELD

After exiting the Framework in last week's episode, the agents return to the real world and all the dangers and challenges that come along with it. In May and Coulson's case, that means they're stuck in a secret base below an oil drilling platform where they must protect Mack while he stays plugged into the Framework and avoid the army of LMD that are being controlled by Anton Ivanov. As for Daisy and Simmons, they're trapped on a quinjet that is severely lacking in basic functions while being pursued by an enemy plane piloted by one of Ivanov's LMDs.

With some help from Aida, May and Coulson are able to get Mack out of the base and all three of them reunite with Daisy and. Simmons. They, and the rest of the quinjet skeleton crew, are the only ones left after the LMD attack on S.H.I.E.L.D. HQ in 'Self Control'. In fact, the world all the agents are returning to is very different from the one they left when entering the Framework because of the events of 'Self Control'. In order to escape the S.H.I.E.L.D. base at the time, LMD-May set off a massive explosion that took out Aida's remaining LMDs. And, since that time, Jeffrey Mace's body was found with no explanation as to his death - other than it looked like Quake had killed him with her powers.

Because all the top S.H.I.E.L.D. agents have been missing for the 10 days following the events of 'Self Control', General Talbot is up in arms when they return. He's still worried about LMDs - and is worried that the agents themselves are androids - while the real problem has shifted to something else entirely. This particular storyline in 'The Return' is a bit jarring, especially since it draws on events that transpired a number of episodes ago, but that drives home how difficult it must be for the agents returning from the Framework to get used to their world. Still, the status of S.H.I.E.L.D.'s reputation in the world and, to an extent, Talbot's worries over LMDs, aren't high priority for the agents as they have a new kind of enemy to deal with in Aida.

Aida's A Real(ish) Girl

Mallory Jansen as Madame Hydra AIDA and Iain De Caestecker as Fitz in Agents of SHIELD season four

While the agents returning from the Framework have to come to terms with the memories of what happened there (and, in May and Coulson's case, what happened prior to their entry into the digital world), perhaps the most compelling character arcs of the episode are Aida discovering what it is to be human, and Fitz trying to help her through it while reconciling his own Framework memories. In fact, Fitz doesn't get much time to process how he could have done the things he did in the Framework, since Aida immediately transports them to a remote location and expects them to pick up where they left off in their relationship.

'The Return' follows Fitz as he tries to teach Aida about empathy and how to conquer emotions like fear in order to do the right thing - like save Mack from drowning in the oil drilling base. There is a bond between Fitz and Aida that carries over from the Framework, and because of his loyalties from the digital world, it's unclear where he'll fall now that he's back in the real world. Will he stick with Aida because he can't bear to return to Simmons after everything he did in the Framework? There's real tension in Fitz's return to the real world because he was the most changed by Aida's tweaks to history in the Framework, and there feels like a real possibility he could betray S.H.I.E.L.D. and Simmons to side with Aida.

Because of this tension, the moment he reveals he can only have one person in his heart, and that person is Simmons, comes as both a shock to Aida and the viewer. Given how Aida has been able to manipulate those around her for most of her existence, Fitz's perceived betrayal of her hits incredibly hard - especially since it's her first heartbreak on top of her first time feeling everything else that comes along with being human. She becomes overwhelmed and goes full villain, tearing through S.H.I.E.L.D. HQ on a warpath, using a number of Inhuman powers that Hydra mined in the Framework. Considering the strength Aida displays in 'The Return', and how hurt she is by Fitz's revelation, she's set up to be a truly formidable foe in the season finale.

Cliffhangers Heading Into the Finale

Ghost Rider Car Banner

The final moments of 'The Return' feature two exciting cliffhangers that Agents of S.H.I.E.L.D. will need to deliver on in next week's season 4 finale. The first is Yo-Yo plugging herself into the Framework in a desperate effort to convince Mack to return to the real world, despite the fact that his daughter isn't alive in reality. However, when Yo-Yo wakes up, she's strapped to a table in what appears to be the Hydra Inhuman testing facility in the midst of a battle. We can presume that the Resistance was able to mount a significant force (thanks to Coulson's message) and led a revolt against Hydra's rule. Where that leaves Yo-Yo and Mack though, remains to be seen.

The second cliffhanger of 'The Return' sees the return of Ghost Rider, who steps through the interdimensional portal created by Aida to get Robbie, Fitz, and Coulson back in a much earlier episode in season 4. He steps through as Ghost Rider, complete with his fiery chain, and looks ready to do battle, but the episode ends before his presence can be discovered by anyone left in S.H.I.E.L.D. HQ.

With Ghost Rider back - though it remains to be explained exactly how he returned from the other dimension - and Aida full of Inhuman superpowers that make her nearly unstoppable (not to mention her newfound human emotions overwhelming her), Agents of S.H.I.E.L.D. has set the stage for an exciting finale. Of course, how it all comes together remains to be seen, but 'The Return' moves all the pieces into place while not feeling too much like a setup episode. Now, Agents of S.H.I.E.L.D. is poised to wrap all of its season 4 storylines up in next week's finale episode, 'World's End'.

Next: Agents of S.H.I.E.L.D. Reportedly Getting Season 5 Renewal

Agents of S.H.I.E.L.D. season 4 concludes Tuesday, May 16 with ‘World's End’ at 10pm on ABC.