If there's one episode of the series that fans of the series absolutely must watch, this is it.
After the dramatic events of the Xindi arc from the third season and the complications of the season premiere, the crew is finally able to begin coping with what's happened to them. In a lot of ways, this is Enterprise's version of "Family," the Next Generation episode that followed "The Best of Both Worlds." Picard had been through a terrible ordeal. As the title of that episode suggests, Picard (not to mention Worf) has family matters he has to handle, especially an older brother who has long been jealous of him and once again breaches the logic of adventuring through the stars, something that has new relevance now that he's just survived being assimilated and causing the deaths of thousands.
For Archer, it's a time to perhaps rethink his prior attitudes about space travel as well. As the first deep-space captain and son of the man who developed the Enterprise's warp engine, he's long fought a sense of entitlement (see: "First Flight") and boundless enthusiasm for the resulting mission that brought him into pioneer territory every day. But the Xindi experience was different. He had to remain strong for the sake of success, and that took an incredible amount of willpower. Now he falls apart.
It doesn't help that an old girlfriend of his pops up. Erika Hernandez will return in later episodes, but for now she's a rare opportunity to glimpse Archer's life before the NX-01. Much of this season spends time revisiting past associations, actually.
The episode also features foreshadowing for another story later in the season. The unexpected fallout of the Xindi crisis was a newfound xenophobia on Earth, something Phlox experiences firsthand. Now, if you've ever watched the series, you know Phlox is one of the most lovable characters in the franchise. And yet he is not loved in "Home." That's a darn shame.
And besides that, arguably the most important element of the episode is T'Pol returning home. Again, there's further ramifications of this, too, throughout the rest of the series. Part of it reflects back on her relationship with Tucker, especially the knotty complications of the previous season. She learns that her mother (like Worf's brother Kurn in "Sons of Mogh") has suffered the consequences of her actions in previous episodes, and the only way to resolve them is to marry the man she was once betrothed to (something that was gone over in the first season).
The only problem is, Tucker still has feelings for her, and so the episode ends bittersweetly with the engineer biting his tongue as the wedding is conducted.
I said at the start of this recap that you should really watch this episode if you love this series. You will probably also love this series if you start with "Home." You'll want to know the rest of the story, because this is one of those continuity stories that explains exactly what to love.
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Memory Alpha summary.