Two girls have an intense fantasy life; their parents, concerned the fantasy is too intense, separate them, and the girls take revenge.

Pauline Parker: She is most unreasonable. Why could not mother die? Dozens of people are dying all the time, thousands, so why not mother? And father too.
Juliet Hulme: All the best people have bad chests and bone diseases. It's all frightfully romantic.
Pauline Parker: [voiceover, from her diary] We have decided how sad it is for other people that they cannot appreciate our genius.
Juliet Hulme: Only the best people fight against all obstacles in pursuit of happiness.
Pauline Parker: [narration] The next time I write in this diary, Mother will be dead. How odd... yet how pleasing.
Juliet Hulme: Affairs are much more exciting than marriages.
[Then, with disgust]
Juliet Hulme: As Mummy can testify.
Pauline Parker: [narrating] We realised why Deborah and I have such extraordinary telepathy and why people treat us and look at us the way they do. It is because we are MAD. We are both stark raving MAD!
Juliet Hulme: Absolutely not! Orson Wells! Urgh! The most hideous man alive!
[Pauline and Juliet are planning to run away to Hollywood and meet their favorite actors, such as James Mason and Mario Lanza]
Juliet Hulme: As soon as those bods in Hollywood cop a look at us, they'll be falling over themselves!
Pauline Parker: Oh, it'll be amazing to meet James in person. I just know we'll hit it off brilliantly. And Guy Rolfe. And Mel Ferrer.
Juliet Hulme: And Mario!
Pauline Parker: Oh, I can't wait to do the love scenes.
Juliet Hulme: Ooh.
Pauline Parker: But what if they're married?
Juliet Hulme: Oh, don't worry about that. We'll simply 'moider' any odd wives that get in our way!
Juliet Hulme: [speaking too brightly of the murder of Honorah Parker Rieper] I think she knows what's going to happen. She doesn't appear to bear us any grudge.
John: [Chasing Pauline on his bike] Yvonne! Stop! I still love you! Yvonne!
[Juliet and Pauline look out the train window at him, and grin to each other]
Pauline Parker: [voiceover] Compared with these two, every man is a fool. The world is most honoured that they should deign to rule, and I worship the power of these lovely two, with that adoring love known to so few.
Pauline Parker: [narrating] This notion is not a new one but this time it is a definite plan which we intend to carry out. We have worked it out carefully and are both thrilled by the idea. Naturally we feel a trifle nervous, but the pleasure of anticipation is great.
[shortly before the murder]
Juliet Hulme: [admiring the view that includes the path down the hill, where the murder occurred] Isn't it beautiful?
Pauline Parker: Let's go for a walk down here. Come on, Mummy!
Honorah Parker Rieper: Oh! No, I'd like a cup of tea, first. Come on!
[the girls reluctantly follow her into the tea-house]
Pauline Parker: Oh, I wish James Mason would do a religious picture! He'd be perfect as Jesus!
Juliet Hulme: Daddy says the Bible's a load of bunkum!
Pauline Parker: But we're all going to heaven?
Juliet Hulme: I'M not! I'M going to The Fourth World... it's sort of like heaven. Only better, because there aren't any Christians!
Juliet Hulme: [Juliet has just arrived at her new school. For French class she has taken the name Antoinette] Excuse me, Miss Waller, you've made a mistake. "Je doutais qu'il vienne" is in fact the spoken subjunctive.
Miss Waller: It is customary to stand when addressing a teacher,
[pause]
Miss Waller: Antoinette.
Juliet Hulme: [stands] You should have written "vînt".
Miss Waller: I must have copied it incorrectly from my notes.
Juliet Hulme: [stands] You don't need to apologise, Miss Waller. I found it frightfully difficult myself until I got the hang of it.
Juliet Hulme: Stick it up your bottom!
[last lines]
[the last lines show scenes of the murder intercut with b&w shots of Juliet being taken away by her parents on the ship. Pauline and Juliet are sobbing and screaming for each other; and the girls scream as they beat Honorah Parker to death]
Juliet Hulme: Gina!
[sobs as she reaches a hand over the ship railing]
Pauline Parker: Juliet, don't leave! I'm coming! Don't go! You can't! Oh, no!
[as the girls cry and reach helplessly toward each other, Juliet's parents come and stand on either side of her, trying to comfort her]
Juliet Hulme: I'm sorry...
[Pauline screams, and the b&w scene fades into the murder scene]
Pauline Parker: No!
[That last bloody shot fades into the credits]
[voiceover; narrated from her diary]
Pauline Parker: There are living among two dutiful daughters - of a man who possesses two beautiful daughters - you cannot know nor yet try to guess, the sweet soothingness of their caress. The outstanding genius of this pair is understood by few, they are so rare.
Pauline Parker: It's a three act story with a tragic end.
Juliet Hulme: Bloody Bill's sniffing around Mummy something chronic!
Pauline Parker: I thought he was supposed to be terribly ill.
Juliet Hulme: That's what we were led to believe.
John: I love you so much Paul. Do you love me as much as I love you?
Pauline Parker: Of course I do, Nicolas.
John: My name is John.
Pauline Parker: Oh, but I like Nicolas so much better!
[Pauline is spending the Easter holiday with the Hulmes. Hilda Hulme, brushing Pauline's hair into an attractive shag, listens while Juliet describes more of the story that they've been devising]
Juliet Hulme: Mummy, Paul and I have decided that Charles and Deborah are going to have a baby, an heir to the throne of Borovnia.
Hilda Hulme: What a splendid idea.
[She grins, while Pauline is ecstatic with the attention being lavished upon her]
Juliet Hulme: We're calling him Diello.
Hilda Hulme: Well, that's a good, dramatic name.
Juliet Hulme: Paul thought it up.
Hilda Hulme: Aren't you clever?
[Pauline beams while Mrs. Hulme fluffs up her hair]
Hilda Hulme: There: all done.
[Pauline jumps up and takes Juliet's hand]
Hilda Hulme: Oh, look at you two. A couple of Borovnian princesses, if ever I saw them! My daughter... and my foster-daughter.
[During a night rain-storm, Dr. Hulme knocks on the Riepers' door]
Dr. Henry Hulme: Mrs. Rieper, may I come in?
Honorah Parker Rieper: Yes, of course.
Dr. Henry Hulme: Thank you.
[They sit in the parlor]
Dr. Henry Hulme: Your daughter's an imaginative and spirited girl.
Honorah Parker Rieper: Look, if she's spending too much time at your house, you only need to say. All those nights that she spends over, she assured us that you don't mind.
Dr. Henry Hulme: It, it's rather more complicated than that. Since Mrs. Hulme and I have returned home, Juliet has been behaving in a rather disturbed manner... surliness, general irritability - most uncharacteristic.
Herbert Rieper: Sure I can't tempt you to a nice sherry, Dr. Hulme?
Dr. Henry Hulme: No, thank you. The thing is...
Honorah Parker Rieper: Yvonne hasn't been herself, either. Locking herself away in her room, endlessly writing.
Dr. Henry Hulme: My wife and I feel the friendship is... unhealthy.
Herbert Rieper: No arguments there, Dr. Hulme! All that time inside working on those novels of theirs. They don't get fresh air or exercise!
Honorah Parker Rieper: I'm not sure what you mean, Dr. Hulme.
Dr. Henry Hulme: Your daughter appears to have formed a rather unwholesome attachment to Juliet.
Honorah Parker Rieper: What's she done?
Dr. Henry Hulme: She hasn't done anything. It's the intensity of the friendship that concerns me. I think we should avert trouble before it starts.
[first lines]
[Director Peter Jackson opens with the scene that should, logically, end the film: that is, the moments immediately following the murder. The girls Juliet and Pauline run screaming up the hill-path to the tea-house, sobbing and covered in blood. The scene is intercut with b&w visions of the two running across a ship deck to meet Dr. and Mrs. Hulme, whom they both refer to as their mother, as the first three exclamations of "Mummy!" demonstrate]
Juliet Hulme: Mummy!
Pauline Parker: Mummy!
Juliet Hulme: Mummmmy!
[the scene changes from the ship to the hilltop tea-house. The girls are screaming hysterically as the tea-house woman runs out to see what the noise is all about]
Pauline Parker: It's Mummy! She's terribly hurt!
Juliet Hulme: Please! Help us!
Pauline Parker: [Narrative from the diary] My new years resolution is a far more selfish one than last year. It is to make my motto, eat, drink and be merry for tomorrow, you may be dead
[Of Pauline's homosexuality]
Doctor Bennett: Chances are she'll grow out of it. If not... well, medical science is progressing in leaps and bounds. There could be a breakthrough at any time!