Innocence

In which Buffy has the worst post-coital regret in the history of sex, Xander has a good idea, Jenny has a dead uncle, and Angel is evil.

Official back-of-box synopsis:

After Buffy and Angel's intimate moment transforms him back into Angelus, Buffy realises she must destroy him. Giles' relationship with Jenny Calendar takes a new twist, and Willow's hopes are dashed when she discovers Xander and Cordelia's secret romance.

From the old WB Buffy website:

THE CONCLUSION OF A SHOCKING TWO PART EPISODE -- After Buffy shares an intimate moment with Angel which extinguishes his human soul, she is left with the realization that she must destroy the now-evil Angel who has transformed into his previous persona of Angelus. Meanwhile, Giles' relationship with Jenny Calendar takes on a new twist when he discovers that she is a member of the gypsy family who gave Angel his human soul, and Willow's hopes of a relationship with Xander are dashed when she discovers Xander and Cordelia's secret romance.

Links:

This episode's page at http://www.restlessbtvs.com/, the Restless BTVS Trivia Guide

This episode's page at http://www.vrya.net/bdb/, the Buffyverse Dialog Database

Cross-reference:

episodes featuring dream sequences:

• Welcome To The Hellmouth
  Buffy's dreaming the very first time we see her
• Teacher's Pet
  Xander fantasises about being a rock god with Buffy at his feet
• When She Was Bad
  Buffy dreams that Giles attacks her
• The Prom
  Buffy and Angel in a nightmare wedding
• Graduation Day (part 2)
  Faith gives Buffy hints on how to defeat the mayor, plus something about 7-3-0...
• Hush
  A spooky little girl with the answer to the mystery of the Gentlemen
• Restless
  The First Slayer invades the dreams of Willow, Xander, Giles and Buffy in turn
• The Weight Of The World
  Buffy's locked in a recurring dream from which Willow has to rescue her
• this episode
  Buffy's dream tells her Jenny's keeping secrets

Cast:

• Sarah Michelle Gellar as Buffy
• Alyson Hannigan as Willow
• Nicholas Brendon as Xander
  

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• Anthony Stewart Head as Giles
• Charisma Carpenter as Cordelia
• David Boreanaz as Angel / Angelus
• Kristine Sutherland as Joyce
• Brian Thompson as The Judge
• Robia Lamorte as Jenny Calendar
• James Marsters as Spike
• Juliet Landau as Drusilla
• Seth Green as Oz
• Vincent Schiavelli as Uncle Enyos
• Ryan Francis as Soldier
• Carla Madden as Woman
• Parry Shen as Student