On a bright day in Tokyo-3, Asuka is simply ecstatic to be shopping with Kaji, who all in all just quietly humors her, and makes a stop at the swimsuit section. The reason is that the school trip to Okinawa is coming up and the class is scheduled to go scuba diving. Asuka brightly asks Kaji where he went for his school trip to which he replies that he didn't have one. As to why, he says, "Oh, just a little thing called the Second Impact."
Back at Misato's place, Asuka pitches a fit at Misato's revelation that Asuka can't go on the school trip because she is on permanent standby as the pilot of Eva Unit-02. Asuka tries to get Shinji to back up her protest, but he calmly replies that he expected something like this to occur. This just gets Asuka even more annoyed and she asks Misato why everyone is always playing defense and why the Evas are not sent to bring the fight to the Angels. Misato answers that if they could, NERV would have already done that. She then tells the two of them to take this opportunity to get ahead in their studies while the rest of the class is on a field trip since their scores on test have been absolutely dreadful recently.
To compensate for not being able to go on the school trip, Asuka decides to take a dive in the swimming pool in NERV HQ. In the meantime, Shinji decides to go over some physics homework. Asuka scoffs at the easiness of it as she learns in over Shinji's computer (giving him a view of her cleavage in the process) and solves the problem quickly. Trying to hide his flusteredness, a blushing Shinji asks her how someone so sharp at math as her are not doing better at the school tests. Asuka reveals that the reason she has been doing so badly is because she hasnt yet learned enough kanji to understand what the questions are asking, since she didn't exactly study much written Japanese during her time at college, casually mentioning that she just graduated last year, when Shinji expresses surprise about her already having attended college. She then asks what the test is actually about, and Shinji explains that its topic is thermal expansion. Asuka brags that it is a rather easy topic, and sums it up with the brief statement that most materials expand when heated and contract when cooled. She then takes this opportunity to tease Shinji further by asking him whether her breasts will get bigger if she makes them warmer. Shinji quickly claims ignorance saying that he doesn't think about stuff like that. Disappointed, Asuka pronounces him "boring" before going off to practice more scuba-diving.
Meanwhile, at NERV, Fuyutsuki, Ritsuko, and the bridge team are analyzing photos taken at Mount Asama. The reason is unknown. Fuyutsuki remarks that the photos are not clear enough, to which Aoba replies that the research team at Mount Asama recommends further investigation. When Ritsuko asks about the Magis opinion, Ibuki replies that the probability is 50/50. Misato is already revealed to be at the research site. She is using a probe that belongs to the research team set up at Mount Asama to investigate the inside of the volcano. As the probe goes deeper, it eventually implodes from the extreme pressure but not before extracting an image from the depths of the volcano. The blood type is blue, meaning that it is the eighth Angel, Sandalphon, albeit in an embryonic state that precedes the normal adult form everyone is used to.
Misato informs NERV of the findings, and the organisation scrambles to plan an attack on the Angel. Gendo meets with the SEELE board members to request an A-17. Presumably, this involves allowing NERV to as much resources as necessary to complete an operation. While the Human Instrumentality Committee is initially hesitant to deal with an embryonic Angel, considering what happened with the Katsuragi expedition, the experiments on Adam, and the resulting Second Impact, Gendo tempts them with the possibility of obtaining a live Angel sample for study. This prompts the Committee to greenlight the operation, but Keel makes sure to warn Gendo that failure will not be tolerated. "If we fail, it will result in the extinction of the human race," notes Fuyutsuki flatly, and asks Gendo if he really is sure about this. Gendo doesn't answer his question; his self-assured smile says it all.
Asuka is chosen to be the one to carry out the mission to capture the Angel, as Unit-02 is the only Eva capable of using the Type-D equipment which is necessary for the task. While she is initially thrilled at the prospect of carrying out the mission, the rather unglamorous appearance of the heat-resistant plug suit and Type-D equipment for her Eva Unit quickly causes those feelings to change. But as Rei volunteers to do the task, Asuka tells her to back off and let her do the job, as she refuses to let Rei touch Unit-02.
Both Shinji and Asuka are deployed with Shinji serving as backup. Asuka is lowered into the magma with a capture device. But as this happens, Shinji notices a bomber flying overhead, and is told by Ritsuko that it is the UN's Air Force who are present as a security measure. In case the Angel escapes from NERV during the operation, it will unload an Nmine on them. He asks who ordered such a thing, and is not too surprised when Ritsuko answers that it was Gendo. Meanwhile, Kaji watches the operation through binoculars from a cable car, talking with a woman, who appears to be a contact of his, who poses incognito as a tourist. She tells him that when the A-17 directive was issued it messed up some plans their employers had been working on, asking him why he didn't attempt to stop it in its tracks, as she reminds him of the dire consequences that would result from NERV make the slightest mistake. Kaji ensures her that NERV aren't arrogant enough to make such mistakes.
After descending to the initial calculated depth of the Angel, Asuka finds that the Angel is no longer there. Ritsuko attributes this is a calculation error involving the magma currents speed. Misato orders the descent to continue, even as the maximum depth allowed for the Type-D equipment is exceeded. The bridge bunnies start to object, pointing out that they are not dealing with an unmanned probe this time, but something with a human being onboard. But their protests subside when Asuka chimes in and confidently says she agrees with Misato and wants to keep going. Finally, at the depth of 1780 meters, the Angel is found and Unit-02 goes in for capture.
Initially the mission seems successful as the electromagnetic cage is activated and Asuka begins her ascent with the Angel. However, during the ascent the Angel begins to hatch out of its egg and the cage cannot contain it. The Angel bursts out and in matter of seconds it matures into what looks like a gigantic Anomalocaris-like creature. Better adapted to the environment, the creature swims around with great agility, attacking Asuka. Since her progressive knife had been lost during the descent, Shinji is forced to throw down his so that Asuka can fight. However, Sandalphons skin has adapted to the extreme pressures of the magma chamber of Mount Asama and so, even the prog knife has no effect on its skin. But suddenly, Asuka gets a flash of inspiration: Using her knowledge of thermal physics, she uses the cut coolant tubes connected to her Eva Unit to cool the Angels skin, making it brittle and vulnerable, killing it in the process. But despite her triumph, she quickly realizes that she is left stranded inside the volcano since the cables connecting her to the surface were severely damaged during the fight. As the cables start to break and the D-type equipment starts to fail from the lack of coolant, Asuka realizes that she is probably going to die and quietly accepts her fate. But suddenly, just as the cable snaps and Unit-02 starts to drift downwards, Unit-01 suddenly appears and grabs it by the wrist. Asuka is surprised that Shinji would jump to her rescue with such disregard for his personal safety, and, in spite of herself, she can't help but be impressed, smiling tenderly as she mumbles, "Fool. What a show off."
Later, the pilots and Misato take a break at a nearby hot springs. As Shinji relaxes in the mens section with Pen-Pen, he cant help but listen to what is happening next door in the womens section where Misato teases and tickles Asuka. As he listens, Pen-Pen starts to notice a particular kind of expansion occurring which Shinji quickly hides in embarrassment. As the two women calm down and relax a bit more, Asuka glances at a scar on Misatos body. Misato notices and tells her that it occurred during Second Impact. Asuka then asks if Misato knows everything about her past which Misato confirms, stating that its part of her job. She states that the past is ancient history for the both of them and they really ought to let it go.
Tropes in this episode include:
- Call-Back: Shinji and Asuka gets the same idea of using thermal expansion to defeat Sandalphon at the exact same time. The synchronization training from "Moment, Heart, Together" apparently still has some lingering effects.
- Chekhov's Lecture: Thermal expansion.
- Did You Think I Can't Feel?: It is a small moment, but it says something. As Asuka comments on Shinji's calm acceptance of the cancelled school trip she calls him a "pathetic housebroken male", he answers, somewhat offended, "Please don't talk about me like that." showing that while he might be willing to put up with a lot, even he has his limits.
- Foreshadowing: The embryonic Sandalphon is strikingly human in its shape, tipping off the fact that humans and Angels are closely related.
- Throw the Dog a Bone: This is the only episode in which we really get to see Shinji in a genuine moment of contentment, in the hot-springs after the end of the mission. It's hard not to feel happy for him yet sorry for him at the same time, given how much pain he's suffered and how much he will suffer in the remainder of the series.
- When She Smiles: Seeing Shinji jumping to her rescue with no regard for his own safety, surprises Asuka enough to get a sincere warm smile out of her.