A man tries to get into the library to see Giles but a demonic woman shows up and strangles him to death. He falls to the floor, and she turns into a puddle of green slime.
At school, we see Buffy and Willow playing the game 'Anywhere But Here', in which they recount their some of their fantasies; Buffy is on a beach before sunset having her feet rubbed by Gavin Rossdale; Willow is in Florence at a restaurant eating ziti when she is joined by John Cusack. Giles tells Buffy to meet him later at the hospital where there will be a blood delivery, which attracts vampires. Giles runs into Jenny Calendar, who invites him for a date that weekend, a date that will involve them "staying in". When a cheerful Giles gets back to the library, a detective is waiting for him—the dead man had Giles' address on him. Giles identifies the body as that of an old friend from London. The body has a tattoo on it, which Giles claims he can't identify.
Shaken, Giles forgets to meet Buffy at the hospital, and she battles the vampires, who are disguised as doctors, alone until Angel shows up. She asks Angel to see that the blood gets to the hospital and goes to check on Giles. When Buffy goes to Giles' house to see what happened, he looks terribly drunk and sends her away. He calls a friend in London and finds out that she's dead, too. He crosses her name off of a list, and we see that several other names have also been crossed off. As he rolls up his sleeves, we see he has the same tattoo as his friend. Meanwhile, the dead friend, Phillip, comes back to life in the morgue, his eyes flashing, and escapes.
On Saturday, Willow, Xander, and Cordelia meet with Jenny Calendar for a computer class. Buffy shows up to express her concern about Giles' behavior. Cordelia mentions the police visit to the library, which slipped her Cordelia-centered mind. In the library, Buffy finds Ethan, the costume shop owner and Giles's former friend, who had almost gotten her killed on Halloween. As she calls Giles, Ethan mentions the "Mark of Eyghon". Giles says she's in danger, and the dead Phillip enters.
A panicked Giles shows up and, after a scuffle which leaves Jenny unconscious, Phillip turns into the green goo. Some of it gets on Jenny and when she comes to, she seems normal but we see her eyes flash. Willow then discovers the "Mark of Eyghon" in a book: Eyghon possesses the body of a dead or unconscious host. They figure out that he's jumped from Phillip's body to Jenny's. Jenny then tries to seduce Giles at his apartment. When he rebuffs her due to her recent trauma, the demon changes her appearance and voice so that it is clear it is no longer Jenny, and attacks. When Buffy comes to the rescue, Jenny/Demon jumps out the window. Giles explains to Buffy that he ran with a bad crowd when he was young, and they used being possessed by Eyghon as a temporary high — directing the demon into and out of each others' bodies. It was fun until Eyghon killed the friend he was possessing. At that point, Giles left the group. More recently, Eygon killed the woman who killed Phillip, and now it seems Eyghon is seeking out the rest of the group to kill, too. Buffy goes to the deserted costume shop to try to help Ethan but he knocks her out, ties her up and puts the mark of Eyghon on her. He then pours acid on his own tattoo so that Eyghon will take Buffy instead of him. Jenny enters, now looking completely demonic, and approaches Buffy. But Buffy breaks free and starts fighting. Angel enters suddenly and chokes Jenny: Eyhgon's spirit then leaves her body and enters Angel's, since he's really dead (which happened to be Willow's plan all along). Eyghon fights Angel's demon, and is beaten. Jenny returns back to normal, but Ethan escapes.
Back at school, Jenny is cool to Rupert, who thinks she'll never forgive him.
- A Day In The Lime Light: For Giles
- Addictive Magic: Giles's Former Teen Rebel status comes to full light - this being Sunnydale, "I used to be a drug user" becomes "I used to let a demon possess me for kicks". Willow's research describes the feeling as a euphoria, which Giles corroborates."It was an extraordinary high. God, we were fools."
- Almost Kiss: Averted; the school bell rings as Jenny and Giles are about to kiss, but they do it anyway.
- Belligerent Sexual Tension: This is the first time Xander and Cordelia are forced to spend significant time together as Scoobies. They're practically about to make out while screaming at each other before Willow interrupts them.
- Beware the Nice Ones: Giles once again lets the Ripper out when Ethan shows up. It worries the people around him. The look in his eyes when he threatens Ethan in the library...
- Bleached Underpants (In-Universe): All of Giles's tweed is his attempt at bleaching his Old Shame.
- Birds of a Feather: Knowing Giles was also foolish in his younger years increases Buffy's bond with him.
- Bittersweet Ending: Everyone important survived, the demon is dead, but Giles and Jenny's relationship took a serious hit.
- Body Surf: Eyghon must switch from host body to host body to survive.
- Bookshelf Dominoes: Ethan tries to knock down Buffy this way.
- Brain Bleach: The Scoobies have this reaction at the thought of Giles and Jenny having sex.
- Conveniently-Placed Sharp Thing: Ethan Rayne has Buffy tied up, with her arms wrapped around the edges of a table and tied together beneath it. There is a conveniently located screw sticking out the bottom of the table that she uses to saw through the ropes.
- Cower Power: Rayne leaps behind Buffy when Zombie!Philip does his Super Window Jump.
- Cut Phone Lines: Jenny does this when she's posessed.
- Dark and Troubled Past: Giles
- Demonic Possession: Eyghon the Sleepwalker can inhabit any unconscious or dead body in his vicinity.
- Dirty Coward: Ethan Rayne
- Drives Like CrazyCordelia: (to the detective in the library) Can you help me with a ticket? It's totally bogus. It was a one-way street. I was going one way!
- Drowning My Sorrows: Giles when Eyghon appears. He works his way through a list of old friends' phone numbers (plus half a bottle of scotch) only to learn they were all dead. His missing an appointment with Buffy for the first time ever is enough to tip her off that something was wrong.
- Evil Sounds Deep: Possessed!Jenny.
- Fantastic Aesop: Demonic possession = drug experimentation.
- Finger-Twitching Revival: Jenny is knocked unconscious when a demon-possessed old friend of Giles breaks out of the library cage...and collapses into a puddle of liquid. As the pool touches Jenny's hand, it twitches, and she comes to... now possessed.
- Foreshadowing: Angel forces Eyghon out of Jenny by choking her. Once inside Angel, Eyghon is killed by Angelus, the demon inside him "just waitin' for a good fight".
- The Gadfly: Miss Calendar likes to tease Giles.Jenny: Oh! Thank you so much for loaning me the Forrester book; it's wonderful.Giles: I'm glad you enjoyed it.Jenny: Yeah, it's so romantic; so... evocative.Giles: That edition was my father's. I must have read it twenty times.Jenny: Yeah, you know how you have to dogear your favorite pages so you can go back to them?Giles: A e a... what?Jenny: I practically had to fold back every single page. So finally I just started underlining all the pages I really wanted to discuss.Giles: U-u-underlined?Jenny: But then, of course, I spilled coffee all over it; I can't even read it...Giles: It's a First Edition...Jenny: I'm lying, Rupert. The book's fine. I just love to see you squirm.Giles: I trust I gave good squirm.
- Getting Crap Past the Radar:Miss Calendar: All right guys, the first thing we're gonna do is— [Buffy enters] Buffy!Xander: Huh? Did I fall asleep already?
- The Glasses Come Off
- Glowing Eyes of Doom
- Gotta Kill Them All: Eyghon's motivation
- Groin Attack: Cordelia shows she is good in a fight after all.
- Hollywood Acid: Even concentrated acid takes time to react with skin. As in minutes or hours. Not the sizzling instants portrayed when Ethan burns off his Eyghon tattoo.
- Idiot Ball: Giles doesn't pull Jennys unconscious body away from the blue liquid puddle even though he should've been aware of the whole Body Surf deal. Had he done that the whole issue would've probably resolved itself then and there since:Willow: [..] Eyghon must jump to the nearest dead or unconscious person to continue living.
- I'll Kill You!Buffy: I'm gonna kill you. Will that blow the whole karma thing?
- It's the Best Whatever, Ever! / Sarcasm Mode: Xander has to attend a Saturday computer class and hears Cordelia does too: "Ooo, did you hear that? An extra day of class AND Cordelia! Throw in a little rectal surgery and it's my best day ever!"
- Kill It with Fire: Ethan burns off his tattoo with acid.
- The Main Characters Do Everything: Angel defeats Eyghon
- Mark of the Beast: The Mark of Eyghon
- Meaningful Echo: Buffy helps Giles get back into tweed-bound character at the end of the episode by encouraging him to say of her jazzercise music, "It's not music, it's just meaningless sound."
- Mood Whiplash: Giles goes from being affectionately teased by Jenny, to being promised sexy-times that weekend, to walking into a library with police waiting to talk with him about an old friend found dead at his doorstep, to Cordelia walking in and demanding help... All in the space of about a minute.
- My God, What Have I Done?
- Nerds Are SexyJenny: Did anyone ever tell you you're kind of a fuddy-duddy?Giles: Nobody ever seems to tell me anything else.Jenny: Did anyone ever tell you you're kind of a sexy fuddy-duddy?Giles: Well, no. Actually that, that part usually gets left out. I c-can't imagine why.
- No Ontological Inertia: The demon Eyghon possesses Jenny, whose appearance gradually becomes demonic. When Eyghon is expelled, her deformities immediately revert.
- Oh, Crap!: Giles has a few over the course of the episode. When he learns that his old friend was found dead on his doorstep, when he learns that all of his friends from that circle are dead apart from him and Ethan, and when Buffy calls him and asks him about the "Mark of Eyghon", and again a moment later when he learns that Buffy is standing next to Ethan, and finally when he realizes that Jenny is possessed by Eyghon. Holy crap.
- O.O.C. Is Serious Business: Buffy realises something is wrong when Giles misses a meeting.
- Old Shame: In-Universe example, Giles used to be a dark magician demon summoning punk rocker. And then his past comes back to kill him.
- Our Zombies Are Different
- Out-of-Character Moment: Willow turns into The Determinator when Xander and Cordelia are about to fight.Willow: Willow: HEY! We don't have time for this! Our friends are in trouble! Now, we have to put our heads together and, and get them out of it! And if you two aren't with me a hundred and ten percent, then get the hell out of my library!
- Revealing Hug: Jenny is temporarily knocked out when a demon-possessed man breaks out of his cell. As a guilt-stricken Giles later holds her, her eyes flash in an "uh-oh" moment.
- Rhetorical Question BlunderBuffy: Have I ever let you down?Giles: Do you want me to answer that, or shall I just glare?
- Shout-Out: To The Lost Weekend, a novel and movie about an author who loses an entire weekend to a drinking binge, when Buffy says she's worried about Giles, not least because he was "lost weekending" in his apartment.
- When Buffy turns off her techno Dance Music, Giles quips "the rest is silence" (the last line from the main character in Hamlet).
- Sinister Silhouettes: Eyghon before he enters Rayne's shop.
- Summon Bigger Fish: Jenny is possessed by a body-hopping demon called Eyghon, who can't be forcibly exorcised without killing her. To get around this, the Scoobies trick Eyghon into jumping into Angel, a vampire. In the Buffyverse, vampires are effectively corpses possessed by demons; the demon already inhabiting Angel's body makes short work of Eyghon.
- Unspoken Plan Guarantee: Willow's plan for defeating Eyghon.
- Villain: Exit, Stage Left: Rayne, naturally.
- The Watson: Cordy fills some of this role, asking questions.Ethan: Hello, Ripper.Cordy: Why did he call him "Ripper"?Giles: [Grabbing Ethan by the back of the head, forcing him to his feet, and threatening him] You should have left when I told you.Cordy: Oh.
- Weirdness Censor: A librarian hangs out with the same few students all the time, these students hang out with him in the library, bring martial arts training equipment there and make a gym out of it with full loud-music-background workouts and nobody really seems to care about it.
- You Won't Feel a Thing: Subverted.Ethan: Now this may sting a little, just at first. But don't worry, that'll go away once the searing pain kicks in.