The two episodes feature vampire slayers Buffy Summers (Sarah Michelle Gellar) and Kendra working to prevent Angelus (David Boreanaz) and fellow vampires Drusilla (Juliet Landau) and Spike (James Marsters) from awakening the demon Acathla.
Giles visits a museum to examine a big stone block that it has just acquired; he finds an opening in the rock.
Buffy and Willow find the floppy disk containing Jenny Calendar's reconstruction of the curse that gave Angelus his soul.
Xander prefers to see Angelus killed, rather than risk leaving him alive merely so that Buffy can have a chance to get her boyfriend back.
Drusilla kills the museum curator while Angelus and his minions steal the stone block, which contains the demon Acathla, who came to suck the world into Hell.
A virtuous knight had stabbed him in the heart before he could draw a breath, but someone worthy can remove the sword to awaken Acathla.
In the library, Willow is attempting the curse, using an Orb Of Thesulah which Giles provided, when vampires attack.
During the fight that ensues Xander is injured and Willow is knocked unconscious under a bookcase while Drusilla hypnotizes and kills Kendra, after which she and her fellow vampires kidnap Giles.
Xander frees the injured Giles and they escape as Spike and Buffy fight against Drusilla and the remaining minions.
At the hospital, just as Willow appears close to fainting, she suddenly regains strength and begins incanting in Romanian.
The score to "Becoming" won Christophe Beck a Primetime Emmy Award for Outstanding Music Composition for a Series.
[1] Vox ranked Part 1 at #14 and Part 2 at #4 of all 144 episodes on their "Every Episode Ranked From Worst to Best" list, writing, "It's all firmly rooted in character, which is what makes each moment lead to the next with such terrible inevitability — and yet it's still difficult to believe that it will actually happen, that Buffy isn't going to pull some brilliant idea out of her back pocket just in the nick of time, that she is actually going to kill her boyfriend.
Club in 2008 Noel Murray wrote that the two episodes are "a marvel, weaving together all of the season's major threads...into a concluding chapter as assured and well-realized as any in TV history.
"[5] Sarah Michelle Gellar, talking to Entertainment Weekly about her personal favorite Buffy episodes, cited this one, along with "The Body," "The Prom," and "Who Are You?"