Buffy vs. Dracula: Dracula comes to Sunnydale and everyone in the Scooby gang assumes one of the parts from Bram Stoker's classic. Obviously, Buffy assumes the part of the character who kills Dracula.
Real Me: Buffy suddenly has a sister called Dawn, and there's absolutely no explanation! Everybody accepts her as having been one of the Scooby gang for ages, and the viewers are distinctly confused. Dawn then accidentally invites a bunch of vampires into Buffy's house, and they promptly kidnap her. But Buffy goes and rescues her, killing the vampires in the process.
The Replacement: In the middle of a fight, Xander is split into two seperate Xanders, one of which has all his positive personality aspects and the other has all his negative ones. Fortunately, he is put back together by the end of the episode, and Buffy doesn't kill any vampires, although she does kill a demon called Toth.
Out of My Mind: Riley certainly is! His body is rejecting lots of chemicals that he was pumped full of during Season 4, but he won't take any treatment for it, leading to hopes among viewers that he might die. Spike realises that he is in love with Buffy. Buffy doesn't kill any vampires, although as I recall, she did have a bit of a tiff with Spike.
No Place Like Home: Buffy finally discovers what Dawn is: she is the Key, something that a super-powerful demon called Glory needs for some reason. Dawn doesn't know this. Buffy tries to kill Glory, but doesn't.
Family: Tara's family show up on her birthday, claiming that she is a demon and say that they have come to take her away. However, Buffy, Dawn and the rest of the gang team up to stop them taking Tara away.
Fool for Love: Buffy is beaten in a fight with a vampire, so she goes to Spike to find out how he managed to kill two Slayers. The majority of the episode is in flashbacks about Spike's past, although we are treated to Riley blowing up a house full of vampires, although, regrettably, not himself as well. Joyce is very ill and has been admitted to hospital for a CAT scan. Spike comforts Buffy.
Shadow: Multiple plot lines going on here: first off, Glory is trying to find the Key, and uses a very poor special-effects snake to do this. However, Buffy kills the snake before it can report back. Joyce's CAT scan reveals that she has a brain tumour and everyone is jolly upset. Riley, meanwhile, is feeling more and more like a spare part and it is increasingly obvious that he will be written out very soon, especially at the end of the episode when Buffy shuts the door on him. It's quite symbolic really.
Listening to Fear: Well, that was good, wasn't it. An extra-terrestrial monster comes to Earth to kill Joyce, but instead Buffy and Spike work together to kill it. Meanwhile, Riley is paying vampires to suck his blood and acting unpleasantly all round, really. Thank Christ he's going to be gone soon. A doctor called Ben reveals to Glory's slaves that he has been clearing up after Glory "his whole damn life". What does that mean, then?
Into the Woods: Spike reveals to Buffy that Riley pays vampires to suck his blood. And he proves it by showing her. Buffy kills all the vampires, comes pretty close to killing Riley and then the two break up (!!!). Riley flies away in a helicopter, and hasn't been seen since, to the best of my knowledge (thankfully).
Triangle: Willow and Anya (Xander's girlfriend who used to be a Vengeance Demon) are left in charge of Giles' Magic Shop while he goes to England to consult the Watchers' Council about Glory. As can only be expected, they let loose a troll who used to be Anya's boyfriend, who rampages around Sunnydale for a while before Buffy defeats it.
Checkpoint: The Council of Watchers come to Sunnydale to assess Buffy and see if she's worthy to get the information about Glory. And of course she is. Glory turns out not to be a demon after all, but a god. Which should make it substantially more difficult for Buffy to kill her.
Blood Ties: Joyce is better and out of hospital, while Dawn, with the help of Spike, finds out that she is the Key. She goes to the hospital (I have no idea why) and meets Ben, who is actually Glory in disguise, although when he is Glory, she has no memory of what happens when she's Ben (or at least I assume so: that's the only way it can be possible for Dawn to confess to Ben in this episode that she is the Key, and Glory doesn't know it mere seconds later). The Scooby gang (and Spike) come along to rescue her from Glory. Buffy, Spike, Giles and Xander all get beaten up, but Willow and Tara teleport Glory to an unknown location (which the viewers find out mere seconds later is very very high up in the sky). And I think that episode synopsis may have been longer than the one for Halloween.
Crush: Spike confesses his love to Buffy, but she rejects him. Drusilla pops up and tries to regain Spike for herself, but Spike instead attempts to prove his love for Buffy by offering to stake Drusilla. Drusilla doesn't get staked and Spike's plan fails. Buffy tells Spike in no uncertain terms to get out of town. Spike doesn't.
I Was Made To Love You: A girl who is looking for a specific boy (by name, but I can't remember exactly what name) throws Spike through a closed window with ease. Despite the pleasure this brings Buffy, she realises that there may be a big problem if this girl does the same thing to an innocent citizen. She finds out that the girl is a robot (which the viewers worked out very early on, it was completely obvious) and catastrophe is averted when the robot's battery runs down. Meanwhile, Glory/Ben is back in town. Buffy comes home to find her mother on the sofa, unmoving ...
The Body: Joyce is dead, but through natural means, nothing to do with Glory. Buffy is distraught, Dawn isn't best pleased either, Giles is supportive, Xander punches a hole in the wall of Willow and Tara's apartment, Tara is reminded of her own mother's death, and Willow can't find the blue top she desperately wanted to wear. Not that Willow's insensitive or anything.
Forever: Angel pops up to tell Buffy he's sorry about her mum but doesn't do anything besides. Dawn enlists Spike's help to re-animate Joyce's dead body, even though she knows resurrection spells can go 'slightly' wrong, and that Joyce might not be quite as she once was. However, Buffy convinces Dawn to break the spell just before the potentially scary Joyce comes back in the house.
Intervention: Glory's minions, mistakenly believing that Spike is the Key, kidnap him. Spike bravely resists their torture of him in order to make him tell who the real Key is, until Buffy and co. turn up to rescue him. As the episode ends, Buffy kisses Spike, telling him that what he did for Dawn and her won't be forgotten.
Tough Love: Glory's minions make another mistake when deciding who the Key is, this time believing it is Tara. Glory, on discovering that Tara is not the Key, sends Willow's unfortunate partner insane. Willow is not very pleased and launches a full scale witchcraft attack on Glory, and nearly wins - but is lucky to get out with her life. As a blatant cliffhanger, when Glory is right there, the now insane Tara reveals that Dawn is the Key. Uh oh.
Spiral: Buffy and the gang flee from Sunnydale to escape Glory. A bunch of knights chase them and corner them in a building out in the desert. On talking to the knights' leader, Buffy and Dawn find that if Glory activates the Key, the barriers between all dimensions will break down and the universe will descend into chaos. Glory captures Dawn and goes off to start the spell, while Buffy sits down, seemingly unable to cope with all the stress.
The Weight of the World: Buffy has totally withdrawn into herself, necessitating a filler episode in which Willow casts a spell to make Buffy better, and we finally learn why no one realised Ben was Glory way way back in Blood Ties - it's because Glory has this spell so no one can remember it after she metamorphises in front of people. Once she's better, Buffy discovers that the only way to defeat Glory is to kill Dawn.
The Gift: Buffy works out that killing herself would defeat Glory, just as killing Dawn would. Consequently, she leaps off a crane into a vast interdimensional portal, which is one of the most ambiguous possible ways to kill oneself, and perhaps explains why Buffy will be returning next year.