Malcolm Reed is the rare Star Trek character who tries to remain as private as possible. That's most of what "Minefield" is all about. That and the Romulan booby traps.
A recurring element of the series and the character throughout Enterprise's four seasons is trying to unscramble the riddle of the weapons officer. In the previous season Reed formed a reluctant bond with Trip Tucker in the standout "Shuttlepod One." Part of "Minefield" plays out like a version of that episode with Archer replacing his engineer buddy. A lot of the second season has the show's characters exploring their own reactions to the unfolding mission of the ship, a contrast to the way relationships formed in the first season and were crucial to the third. Reed's continued standoffishness is a testament to this theme, and is an important part of the unfolding season, which mostly sticks to standalone episodes, the only season of the series to do so.
Yet it's this episode that begins Enterprise's truncated flirtation with the Romulans, which has its brightest moments in the fourth season. Franchise fans knew that there were rules the show needed to follow in order to maintain continuity, and "Minefield" is one of the more clever instances where continuity is maintained while the show still gets to do something interesting with established features of the Star Trek landscape. It helps immensely that the episode balances the danger of the Romulan munitions with the one character who will be able to properly appreciate them, except in these circumstances.
What I'm trying to say is, "Minefield" makes no bones about what exactly is happening and that the Romulans are definitely involved. Sometimes Enterprise wasn't so good articulating these points. Yet because of the limitations of Romulan availability to take an active role in the plot, we instead focus on Reed, and how he needed to be rescued from being literally pinned by a mine to the hull of the ship. Only at this point in the Star Trek television experience could an episode feature a situation like this, though the series pulled them off very sparingly.
Reed is still pretty much a cold fish by the end of the episode. He's a character that risks alienating the audience as much as his colleagues, so it's a little tricky building an episode like this around him. It works as much as it can, and to the extent that you end up caring for him. Strangely, I think he's more sympathetic in other episodes, even though this is the worst situation he ever finds himself in. For that reason, I cannot rate this otherwise standout episode to the full measure, but opinions may differ. I do genuinely like Reed as a character, however, so I have little trouble recommending "Minefield." There's always the Romulans.
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Memory Alpha summary.