overview: the senshi fight a very powerful evil, new senshi are met, and sailormoon levels up!
villians: the deathbusters: professor tomoe, kaolinite, the witches 5 (eudial, mimete, tellu, viluy, and sisters cyprin+puchirol), and mistress nine.
summary: it's after the r season, and everthing is going well. all of the inners are busy studying for their high school entrance exams. they all want to go to juuban high (all but mars, eh...), so they all study at rei's temple. suddenly, rei gets a strange vision: the senshi are frozen, and the world is being completely destroyed.
that same episode, rei is attacked by a terrible new monster, that steals her "heart crystal". it traps the inners and tuxedo kamen, and breaks sailormoons transformation brooch. which sucks. they are saved by the two shadowy figures you see at the end of R.
in the next episode, sailormoon still can't transform. mamoru and usagi stand together, though, and create a new sceptre for sailormoon, which gives her a new attack and improves the transformation brooch, allowing her to transform. you meet sailoruranus and sailorneptune, but they're mean.
soon, you meet haruka and michiru, a cute couple who are nice to the inner senshi. after minako and usagi chase haruka around for a while thinking she's a foxy young bishounen, they are bummed to find out that "he's a hunksterette!" in the words of sailormars, S dub. and yet they have no clue that haruka and michiru are uranus and neptune.
chibiusa becomes a senshi, even though she's truly USELESS. she also befriends hotaru tomoe.
after kaolinite is "killed", the witches five start up. eudial, a very poor dirver, is the first. she exposes the three talismans, but she gets killed by mimete when acidic/toxic snals are put in her car and eat away the breaks. this is where sailorpluto comes in, introdicing the third talisman. neptune hold the aqua mirror, uranus hold the space sword, and pluto holds the garnet orb. the talismans join together to form the holy grail (purity chalice in the dub), which belongs to sailormoon, enabling her to become supersailormoon. mimete gets killed by tellu. tellu is killed by her own plant, and viluy is killed by her own nanobots. next comes the witch cyprin. kaolinite has been revived, and is very much in love with the professor. i mean, madly in love. viluy is very mean to kaolinite, saying that she was only braught back to hang on the professor's arm. she is hurt, but is determined to please the professor. he tells her that she is the only one he can count on, the only one for the job. but, he tells the same thing to cypin, and kaolinite hears it. kaolinite gets really irked, and is determined to get the crystal that will awaken mistress nine. cyprine and puchirol are nearly unbeatable because every attack the senshi use make THEIR attack stronger. mercury casts her fog, and jupiter takes down cyprin and mars takes down puchirol. the witches chase each senshi, eventually getting on opposite sides of each other. they strike at who they THINK are the senshi, but the senshi dive out of the way. in the end, cyprin and puchirol, the invincible sisters, kill each other.
in the meantime, kaolinite has taken chibiusa's heart crystal, and ta-DA! mistress nine is awakened. kaolinite is about to say something (perhaps a declaration of love?) to the professor, when mistress nine kills her, stating that her job is now over. (which was extremely sad, being that kaolinite was only doing evil deeds out of her love for the professor. sniffle.)
mistress nine disguises herself as hotaru, and tricks sailormoon into giving up the holy grail. mistress nine then destroys it, giving its power to pharaoh 90. the inner senshi are locked out of the fight, they are on the outside to prevent the monsters from getting out of control. pluto is out of the picture because she stopped time, "the greatest taboo." sailorsaturn appears to revive chibiusa, and then goes in to kill pharaoh 90, even if she will kill herself as well. sailormoon tries her hardest to become supersailormoon, but because the holy grail has been destroyed, she can't. finally, all of the senshi lend their power, and sailormoon uses her own pure heart crystal to bacome supersailormoon. pharaoh 90 is killed, but supersailormoon has been able to survive it and ressurect hotaru as a baby. all of the senshi live, and everything is peachy.
uranus and neptune decide to be morons though. they thought that what sailormoon did, when she gave up the holy grail, was inexcusable. they wanted to fight her to see if she really was the messiah (as in princess serenity, not jesus). she won, and yes, of COURSE, she is. sailorneptune and uranus pledge their loyalty and leave.
in the manga, professor tomoe dies. in the anime, however, he only gets really bad amnesia. he and hotaru are reunited, and all is well.

special notes:
in the manga, professor tomoe dies. that is why haruka, michiru, and setsuna raise baby hotaru. in the anime, he doesn't, and hotaru is returned to him. so i haven't an idea as to how they got ahold of baby hotaru.

the midi you are listening to is tuxedo mirage, the ending theme of the S season.