One of my favourite episodes of Season 2 along with "The Fisher King Part II", "Revelations", "Profiler, Profiled", "North Mammon" and "The Boogeyman". This said, Season 2 was a strong season, one of the better 'Criminal Minds' seasons in general, where only "Honor Among Thieves" was average at best.
What immediately drew me in with "Sex, Birth, "Death" were the story and the performances of and chemistry between Matthew Gray Gubler's Reid and Anton Yelchin's Nathan Harris. The story is one of the season's most disturbing (along with "Revelations" and "North Mammon"), but it is also one of the most thought-provoking and most emotional, also one that is not as obvious as one would think. A wonderful job is done exploring Harris' inner struggles and Reid's insights and instincts to help him, and it is easy for the viewer to empathise.
The chemistry between Gubler and Yelchin was crucial in making the episode work and that their chemistry is so riveting, so empathetic and tense is one of "Sex, Birth, Death's" many allures. The character of Reid and Gubler's acting were always one of the high points of the show, and helped make underwhelming episodes watchable, Reid is a sympathetic and likable character here and Gubler's acting is fantastically nuanced. Yelchin's performance is indeed gut-wrenchingly superb, being scary and heart-wrenching.
Despite the strong emphasis on these two, the rest of the characters are by no means neglected. The chemistry and dynamic within the team is adorable and charming and Garcia and Hotch are interesting too.
Visually, there is much style, class and atmosphere, while the direction is taut and accommodating and the music haunting and melancholic. The script is thought-provoking and beautifully balanced and the story compelling in its suspense and emotion. The acting is very good, with Gubler and Yelchin dominating.
Concluding this review, classic 'Criminal Minds' and one of the best episodes of Season 2. 10/10 Bethany Cox