When Marvel's Agents of S.H.I.E.L.D. premiered in 2013, it sagged under the weight of everyone's expectations. It was the first Marvel television series to come out of the cinematic universe, and its promise of bigger and better action TV than ever was doomed to disappoint.

Now that it has gained some distance from the initial disappointment, though, S.H.I.E.L.D. has refocused and reenergized to become a much stronger show. Its October 27 episode, "4,722 Hours," exemplifies S.H.I.E.L.D.'s recent commitment to developing its characters beyond their stock descriptions and taking bigger risks besides.

The second season ended on a jarring cliffhanger, as Agent Jemma Simmons (Elizabeth Henstridge) was sucked into a mysterious monolith's surprise porthole. When the third season opened, months had passed, and Simmons was still gone. While she managed to get back, thanks to some canny collaboration with her best friend and lab partner Fitz (Iain de Caestecker), Simmons was shaken by her time on the other side, traumatized by something she couldn't quite articulate. She didn't say anything specific about this horrific experience — until "4,722 Hours."

Almost the entire episode takes place on the hostile planet Simmons was stranded on. It's a desolate, lonely place. It offers no easy answers, nor any real explanations. Every so often, a sinister hour count fades onto the screen. Simmons doesn't know how long she will be there, and her desperation becomes more and more visceral, carrying her through several breaking points.

Of course, we know exactly how long Simmons will be stuck in this frigid hell: 4,722 hours, and not a minute less. But even knowing that she eventually gets back to Earth doesn't lessen the tension in her trying.

Simmons's story could have been told in flashbacks, but instead it gets ample time to breathe

No one would have batted an eye if S.H.I.E.L.D. had decided to tell Simmons's story in abbreviated flashbacks, which are handy devices for delivering a lot of information quickly without disrupting the present day too much. Instead, the show devoted an entire episode to it, allowing us a more intimate look at Simmons's trauma to help us better understand her current headspace — and how hard it will be for her to pull herself out of it now that she's back on Earth.

Henstridge rises to the occasion of portraying Simmons's struggle as it evolves over a period of six turbulent months. There are the first few confused hours, when Simmons is sure that she'll be back in no time if she just sits in the same place. Then there are the panicked hours, when she allows herself to consider that she might be stuck here for a long time.

The thousands of hours afterward go by quicker, thanks to necessity and an unexpected ally in Will Daniels (Dillon Casey), an astronaut who has been stranded there for 14 years. His introduction speeds things along, and not just because Simmons finally has someone (handsome) to talk to who's not a picture of Fitz on her phone (which Fitz rejiggered to have a longer battery life than your average phone).

Simmons and Will's reluctant partnership soon becomes an enthusiastic one (they are the only two people here, and, again, he's handsome), and then the hours start hurtling closer and closer to that magic 4,722 number we know will be the last.

But the enormity of what has happened to Simmons, and what continues to happen to her as she fights for survival, never fades.

"4,722 Hours" is unlike anything S.H.I.E.L.D. has done before — and it should only encourage more episodes like it in future

Director Jesse Bochco alternates close-ups on Simmons's face, alternately determined and desperate, with long shots of her stranded on the planet's desolate terrain. The blue tint overlaid on the California desert is a little cheesy but striking. Simmons's increasing despair is mirrored in the overwhelming dark of this planet, which apparently lies so far away from any sun that there is never any natural light.

The blue is oppressive, but still beautiful in a melancholy sort of way. And as the A.V. Club's Oliver Sava points out, any break in the blue is a significant event, signaling new phases in Simmons's 4,722 hours of near solitude:

The red of the flame Simmons makes to cook the "plant monster" that tried to drown her is the first visual indicator that things are getting slightly better for her, and even though she wakes up in a cage on hour 761, the warm brown of the cave announces that this is actually a positive development. Anything that gets her away from that harsh blue is a plus.

Even aside from its look, "4,722 Hours" is a sharp departure from S.H.I.E.L.D.'s usual structure. What is usually a superhuman procedural becomes a solo survival mission, patient and devastating. Once Simmons and Will learn to trust each other, the mission is kicked into high gear, with Simmons using every ounce of her considerable scientific smarts. As Sava also says, the closest recent relative to "4,722 Hours" is The Martian, but that film still cuts between its stranded astronaut and the many people on Earth trying to get him back.

In this episode, we are firmly and entirely entrenched in Simmons's narrow point of view. She talks to her phone, making voice memos for Fitz. She claws her way up sand dunes, sprints over the planet's cragged surface, sobs into the air and, eventually, Will's reassuring chest. By keeping the perspective limited to Simmons and Simmons alone, Henstridge and writer Craig Titley get to immerse us in this new and terrifying world she had to navigate for more than six months. While "4,722 Hours" works as a standalone episode, it will also change the way we see Simmons once we're back in the S.H.I.E.L.D. labs for good.

Agents of S.H.I.E.L.D. is a complicated show that continues grow even more so. With the cinematic universe lurking at its corners and the renewed exploration of Inhumans, the series is packed, even throughout a 22-episode season. And this episode introduces plenty of clues for future, like the fact that NASA explored the Monolith in 2001 (get it?). But by taking the time to develop Simmons's story and explore something different, both physically and emotionally, from anything it has explored before, Agents of S.H.I.E.L.D. found a way to honor its own voice while trying something completely new.