The Daria Episode Guide:

Death or velvety green? Homicidal houseplants next, on Sick, Sad World.

Mystik Spiral has a gig in a grunge club, which Daria and Jane go watch. Jane gets Daria to go out for a burger with the band after the show. Daria runs into Brittany at the bathroom in the club, who has dyed her hair black, apparently in attempt to start a relationship with someone at the club. Brittany notices that Daria is getting a rash, and Daria gets her to go tell Jane that Daria had to leave. Daria narrowly avoids Trent and Jane by ducking out the emergency exit and catching a cab home.
Helen and Jake are watching some sort of drug-war video or show, and Jake quickly become convinced that Daria is using drugs.
Daria's rash is gone by the next morning, and Jake tries to have a heart-to-heart talk with Daria about drugs. Jane shows up and they walk to school together, and Daria tells Jane about the rash.
Daria starts getting the rash again in Mr. O'Neill's class, and runs out. Mr. O'Neill asks if anyone else wants to be excused because of the emotion of the subject matter (he was talking about King Lear and cuddly tyrants), everyone else leaves too.
Daria meets Quinn in the bathroom, and Quinn tries to help her. Daria goes to see Nurse Chase, the school nurse. Helen calls Jake to have him go get her (although he's still worried about drugs) to take her to the doctor's appointment Helen had her assistant set up.
The doctor (Doctor Davis) thinks she has some sort of allergy, but wants to check her into the hospital anyway. Daria doesn't want to, but Jake forces her to anyway. Daria gets put in a room that hospital staff keep saying vague things about Mrs. Sullivan and changing the subject. Daria sends Jake off for a can of root beer (for himself) and calls Jane to tell her what's happening, and asks her not to tell anyone else. Helen and Quinn show up, and Helen immediately starts bossing everyone around.
Brittany starts looking for Daria, while trying not to appear to, so of course she just goes up to Jane and asks. Jane actually starts telling Brittany what's going on with Daria before she remembers her promise and changes "rash" to "rare condition" and starts telling Brittany about "brain fever."
Helen bullies a doctor (Doctor Phillips) into checking in on Daria, and he seems a little freaked out about the room (like a previous staff member had) before hiding it. He kicks everyone else out of the room so he can talk to Daria alone, mostly to give Daria a break from her parents.
That night Daria has a dream about Mrs. Sullivan, who takes her spirit on a journey to heaven, where everyone complains about getting a brain, so she gets dropped a hole in the clouds and wakes up.
Brittany starts telling people (Kevin, Jodie, and Mack are first) about Daria's "brain fever." Jodie and Mack make fun of her for a bit, but then Brittany lets slip that Daria's in the hospital (during a long, confused rant about deals).
Jane goes to visit Daria in the hospital. Then Brittany shows up to confess about the deals. Then Jodie and Mack show up. Then Quinn shows up looking for the cute doctor. And then Kevin shows up. Then Mrs. Sullivan shows up, looking for an enema bag.
Daria gets out of the hospital, and the doctor thinks her rash is probably caused by anxiety. Daria thanks her parents for being there for her before going out with Jane. Both Jane and Trent show up, and her rash comes back.

Daria: I just need to go to the bathroom.
Jane: Good idea. Check your lack of makeup.

Jake: You don't think Daria...
Helen: Jake, she was never happy, vibrant or involved.

Jane: It was a rare opportunity, getting to hang out with Brittany in a grunge club. Although her hair did leak onto my shoes.
Daria: You sure that wasn't her brain?
Jane: No. There was too much of it.

"Anyway, the important thing is that instead of going to your friends for help you ran screaming into the night." -- Jane ("Ill")

"Skin care crises transcends personality conflicts Daria, it's in the Fashion Club bylaws." -- Quinn ("Ill")

Brittany: She hasn't told you anything... interesting about me, has she?
Jane: No one's ever told me anything interesting about you.

Doctor Phillips: Pleased to meet you. Friend, not family, right?
Jane: How can you tell?
Doctor Phillips: Daria seemed happy to see you.

Wraith's Ramblings:
This was a curiously flat episode. Somehow Brittany managed to monopolize the good bits, but then again, it was written by the same, er, person who gave us "Quinn the Brain" so we have to be thankful it wasn't worse. Aside from the obvious shipper fanservice, this is an episode best left alone.
Also see my Rambling of 10-22-00.

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