Earshot

In which Buffy knows what everyone but Angel is thinking. And it's killing her. No, literally.

Official back-of-box synopsis:

After a vicious fight with a couple of demons, glowing demon ooze seeps into Buffy's skin. At first she is not pleased to learn what has happened... until she starts to have fun with her new-found powers.

From the old WB Buffy website:

PENNY FOR YOUR THOUGHTS - A near-fatal run-in with a pair of oozy, mouthless demons unexpectedly leaves Buffy with the awesome ability to hear other people's thoughts, but this newfound power ultimately threatens to overwhelm and destroy her as the cacophony of thoughts isolates her from the rest of the world and drives her to the brink of insanity. When Buffy's clairvoyance unearths a potential mass murder plan at the school, Giles, Willow and the rest of the gang spring into action to locate the would-be killer and thwart a schoolyard massacre, while Angel endeavors to keep Buffy from spiraling into telepathy-induced madness.

Cross-reference:

episodes with gay themes:

• Phases
  Larry is accidentally outed in the search for a werewolf
• Doppelgangland
  Willow's alter-ego is 'evil and skanky and kinda gay'
• Conversations With Dead People
  Holden informs Buffy that her ex, Scott, has come out.
• this episode
  Larry's now so out he's got his grandma fixing him up with guys

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
• Kristine Sutherland as Joyce
• Seth Green as Oz
• Danny Strong as Jonathan
• Larry Bagby as Larry
• Alexis Denisof as Wesley
• Ethan Erickson as Percy
• Keram Malicki-Sanchez as Freddy
• Justin Doran as Hogan
• Wendy Worthington as Lunch Lady
• Robert Arce as Mr Beach
• Molly Bryant as Ms Murray
• Rick Miller as Student
• Jay Michael Ferguson as Another Student
• Lauren Roman as Nancy