Excepting two disappointments in the still above average "Wanderlust" and "Stocks and Bondage", the previous episodes of Season 1 of 'Law and Order: Special Victims Unit' were of a high standard. The standouts being "Payback" (rare for the very first episode to be one of the best epsiodes of the first season for shows), "Uncivilised" and "Stalked", all three of which were outstanding with the tension of "Stalked" really standing out.
"Closure" to me is one of the better episodes of the first half of the season, of the ten episodes up to this point of it it's in the top 5. It is a great example as to how 'Special Victims Unit' was so good early on. If you are more familiar with the more often aired mid-show/latter season episodes and have not yet seen the early seasons, am going to recommend doing so being someone who personally thinks the earlier seasons are better.
Did feel that the Olivia and Cassidy subplot didn't add very much to the story, other than being an attempt to give some development to the two of them. It did feel somewhat out of the blue as well, with it being the first time it was even mentioned in any shape or form.
Absolutely loved the case however. If that subplot was excised, "Closure" would have gotten a perfect score for the case alone, it was that good. If anybody thinks that the ending feels abrupt or the episode feels incomplete it's because it is actually the first part of a two parter, the second part being the third episode of Season 2. It is a harrowing and poignant case, as well as realistic, with the most revealing thing about the episode being how it shows everything that a rape victim has to go through in the aftermath and how detailed the process is.
Harper is a very well developed character that one feels a lot of sympathy for, both in the early parts and when she hardens (especially the latter actually). One roots for her closure and while some may find the outcome frustrating there is a painful realism to it too. The writing is taut and thought-provoking, with great emotional impact.
Visually, it is slick and gritty while the music is unobtrusive and not constant. The main theme is memorable. Mariska Hargitay shines in her sympathetic chemistry with Tracy Pollan, who is really quite excellent as Harper.
Summarising, absolutely great. 9/10