(Scene opens up showing buildings in England.)
Lawrence: Ooh! Merry old England. How I love our yearly holiday to my parents' home. Big Ben, Buckingham Palace, oh, the White Cliffs of Dover. Stonehenge.
Phineas: Either I’ve grown a lot in the last year, or England's gotten smaller.
Lawrence: Here we are. The old homestead.
Candace: Look! There's Grandma and Grandpa Fletcher.
Phineas: Grandpa! Grandma!
Grandpa Reg: Ahh! Phineas, Ferb! My boys!
Grandma Winifred: Oh, Ferb, you're looking more like your grandfather. Just look at that resemblance. What do you think, dear?
(She places a fake mustache and hairpiece on Ferb)
Grandpa Fletcher: He's a right handsome lad, he is.
Grandma Fletcher: You can keep these. I've got loads of them.
Candace: Hi, Grandpa. Hi, Grandma.
Grandpa Fletcher: Candace? Can that be you? You look like a right beauteous princess.
Candace: Thanks!
(Car honking)
Lawrence: Ta-ta. We're off to the antique convention. See you tonight.
Phineas: Hey, Gramps, what's that cool castle next door?
Grandpa Fletcher: Oh, aye, that's our neighbors, Lord and Lady Pipping. It used to belong to the Black Knight.
Phineas: The Black Knight?
Grandpa Fletcher: Such a wonderful tale of valor.

(Song: "Ballad of the Black Knight")'
The Black Knight of Worcestershire
Some say it's "Worcester-sheer"
Went out to fight the dragon
No one else would volunteer

The Hounds of Heck chased after him
Through all the moors and lands
Because his suit of armor
Was recycled dog food cans

The Black Knight of "Worcester-sheer"
Some say it's "Worcestershire"
He rode off with his Hounds of Heck
To face the dragon's fire!

Grandpa Fletcher: Here, immortalized in bronze, is the Black Knight himself and his Hounds of Heck on their final charge to vanquish the dragon. And here is the disastrous results. (Reginald leads the boys to a statue that shows the dragon with forks and knives, while the black knight is being cooked) Legend says that the Black Knight's ghost still haunts these foggy moors, riding in search of the dragon, followed by his pack of fierce hounds.
Phineas: Hey, I know what we should do today. Grandpa Fletcher, let's have a medieval tournament just like the knights did in the days of yore. We can he jousting and catapults and not bathe.
Grandpa Fletcher: Way ahead of you on the not bathing.

Candace: (Sighs) Man, Stacy, everything here is so old, wet and small, and... and...
Charles: En garde, Stubbings! Ha ha! Come on, man! Parry and riposte. (laughs) I've run you through, Stubbings.
Stubbings: Yes. Delightful, Master Charles. Clearly, you have mastered the rules of tennis.
Candace: Uh, Stacy, I'll call you back.
Stubbings: I believe it's my serve. Oh, dear. I have punned.
(Charles laughs)

Phineas: (Dressed as a fool) Back it up! Back it up! (Trucks beep) Good. Right there. Lumber over here, suckling pigs over there. Hold it! That pig's barely suckling. What do I look like, a fool? (The man carrying the pig shoves an apple into the pig's mouth) That's what I'm talking about. Carry on. (To Ferb) So, you ready to chop some lumber, Ferb? (Ferb salutes) Hey, where's Perry?

(At Perry's lair...)
Major Monogram: Ahh, Agent P. Sorry about the tight squeeze, but they're on the metric system. Doofenshmirtz is attending an evil scientists' convention in London. We're sending you in undercover, disguised as evil scientist Dr. Lloyd Wexler who, incidentally, is the man sitting next to you. Good luck, Agent P.

(Back in England Phineas is building a horse)
Candace: Phineas?
Phineas: Oh, hi, Candace.
Candace: What do you think you're doing?
Phineas: I think I'm building a horse.
(The horse whinnies)
Candace: There's a cute boy next door, and I don't want you guys scaring him off by acting like complete freaks.
Charles: Beg pardon?
Candace: Hello. (Giggles)
Charles: I'm Charles Pipping the fourth.
Candace: I'm Candace Flynn... the First.
Charles: So, what's all this?
Candace: This? Uh... This is just a--
Phineas: We're putting on a medieval tournament.
Candace: Medieval tournament? That has to be, without a doubt, the most--
Charles: Brilliant idea I've heard in years!
Candace: Exactly. (Laughs) Because who doesn't love whatever happens at one of those... Those... Things?
Phineas: Wanna join us?
Charles: Absolutely. We could use my family's castle as a backdrop. And you can be the fair princess in the tower, waiting to be rescued by a handsome knight.
Candace: (she blinks twice) Okay!

(At Evil-Con)
Man #1: Welcome to Evil-Con, Dr. Lloyd Wexler. Hey! Wait a second. (Moves ID card to reveal Perry disguised as Dr. Wexler) You didn't get your evil button. Enjoy the convention, Dr. Wexler.

(At the castle)
Candace: (With a fake British accent) As the fair princess in the tower, I declare Sir Charles the winner of the tournament... (Thinks using her normal voice) Wait a second. Could this be one of those things that backfires horribly on me? (Pauses) Nah.
Charles: Looks like that armor is big enough for the two of you.
Phineas: That's a great idea. (To Ferb) Ferb, I'll take the top half because I tend to do more of the talking, and you take the bottom half because of your incredibly long, willowy legs.
Candace: Yoo-hoo! Sir Charles! They can't even hear me up here. (She yells) Yo, Chuck! (Growls) What is going on down there? (She attempts to open the door, but only manages to pull the handle off) Oh, come on! Hey, guys! I am locked in the tower!
Phineas: That's the spirit, Candace! You sound like a real damsel in distress!
Candace: (She growls) I have got to get out of here. (She tries to grab a spear from a knights grip) Let go! Come on, let go! Fine! Have it your way. (She picks up the armor, and smashes through the door. However, soon after the armor becomes undone, and Candace lands in it, making her look like the Black Knight)

Charles: Well, then, since you chaps are just about put together, I think it's time I popped next door to fetch my own armor.
Phineas: There's something almost disturbing about this. Hey, look. he's back.
Candace: (Grunts)
Phineas: Okay, Charles, we'll help you get on your horse and do a practice run.
Candace: (Muffled scream)

(At Evil-Con)
Doofenshmirtz: You didn't think I'd recognize you, did you? But I do! You’re Dr. Lloyd Wexler, my greatest hero in all of evil science. Oh, I can't believe I'm actually talking to you! You know, I wrote my thesis on one of your early ransom notes. Gee, you wouldn't mind if I just hung around with you today, would you?
Perry: (He blinks twice)

(At the castle)
(Horn salute)
Grandpa Fletcher: Lords and ladies of the court, I declare that this contest is to begin!
Grandpa Fletcher: Are you boys ready over there?
Phineas: Ready, Ferb?
(Ferb opens a compartment in the armor to give a thumbs up)
Phineas: We're ready, Grandpa!
Grandpa Fletcher: How about you, Charles?
Candace: (Muffled screaming)
Grandpa Fletcher: That's the spirit.
(Phineas and Ferb, and Candace begin their jousting match. Candace's horse however bucks her off, sending her into a catapult)
Phineas: Look, our catapult works.
(Cadence gets launched into the castle, but falls down the tower, and back onto the horse, who, in turn, bucks her off, repeating the cycle)
Grandpa Fletcher: Way to hang in there, Charles.
(Candace's horse runs off with her on it)
Phineas: Guess we won, Ferb. Yeah!
Charles: What ho, chaps. Still up for a bit of a joust?
Stubbings: Your lance, sir.
Phineas: Charles? Then who's that?
Grandpa Fletcher: Perhaps it was the ghost of the Black Knight. But I wonder where his Hounds of Heck are.

(Instrumental version of "Ballad of the Black Knight" playing in the background)
(Candace's horse continues to run down the street, causing a gravy truck to crash, spraying her with it, while also releasing dogs from an animal control van)
Man #2: (Upon seeing this) It's the ghost of the Black Knight and his hounds of Heck!

(At Evil-Con)
Doofenshmirtz: It makes me so happy to be surrounded by so much evil. Oh, look! It's your autobiography. It’s always been a dream of mine to have you read it to me. (He pauses) Oh, wait, wait, wait, wait! (Pulls out a teddy bear) Okay, now I'm ready.
Doofenshmirtz: (laughs) Come on! Don't be shy. Paragraph 4. "Upon an evil winter's heart." Go ahead.
Perry: (lip-syching from the book on CD) "Upon an evil winter's heart, the heavy hand of regret infrequently alights. The malevolent path is one trod without the cumbersome shackles of sentimental introspec... spec... spec... spec... spec... spec... spec..." (He whacks the CD player with the book)
Doofenshmirtz: Hmm, that's funny. I don't remember you saying "spec" so many times. (Perry rips off his disguise) Dr. Wexler, you're a platypus. (Perry, looking annoyed, puts his fedora on. Doofenshmirtz gasps) Perry the Platypus!
Doofenshmirtz: I want to say that I knew it was you all along, but I can't because I didn't. So now, I guess I'm supposed to surrender, which I might do if we weren't standing IN THE MIDDLE OF AN EVIL WEAPONS EXPO! (He runs to the giant robots, and gets in one) Ah-ha! Perry the Platypus, your giant robot dragon is no match for my giant robot... Queen Elizabeth I. Hmmm. W- Would you mind switching robots with me? Would you mind too terribly? Please? (They switch robots) Thanks. Thank you very much. I just prefer this one. Thanks. Now, Perry the Platypus, your silly, girly Queen Elizabeth I robot is no match for my giant, fire-breathing... (Perry's robot shoots a laser blast at Doofenshmirtz) Ow! Ow! Wait! I didn't know she had laser eyes. I want to trade back. (Perry sends a punch at Doofenshmirtz) Oof! Well, yours may have laser eyes, but mine breathes (The dragon robot shoots fire from behind Doof) f- (He screams as the fire rushes past) (The dragon robot stops shooting fire) That was a stupid design.

(At the castle)
Grandpa Fletcher: Commence with round Two!

(With that, Charles, now wearing his knight helmet, charged towards Phineas and Ferb with his horse. This time however, Phineas and Ferb found themselves on both sides of their armor, with their heads sticking out from where the hands are. )
Phineas: Uh, oh! Ferb, I think we put it on sideways this time.
(The two horses crash into one another)
Grandpa Fletcher: It's a draw!
(The crowd cheers)

TV Announcer: This just in: A giant mechanical Queen Elizabeth I and a dragon are rampaging through the country engaged in an apparent duel to the death. And in other news, a new version of Jane Eyre is in the offing.

(the robots continue fighting)
Lawrence: (Reading from a newspaper inside a taxicab driving past the fight) Good heavens, look at that! They're making a new version of Jane Eyre.
Doofenshmirtz: (Laughs) Obviously, your Queen Elizabeth I is no match for my dragon! (The Queen Elizabeth robot breaks the headlock she was in) That Queen Elizabeth is a tough old bird.
(Perry continues to wail on Doofenshmirtz, until, Doofenshmirtz accidentally pushes a button)
Computer: Thank you for pressing the self-destruct button.
Doofenshmirtz: Oh, that's just great!
(He slams down on the console)
Computer: Thank you for pressing the ejection button. Remember to take a parachute with you.
Doofenshmirtz: Now you tell me!

(At the castle)
Charles: Look, everyone, it's the ghost of the Black Knight.
Phineas: I guess he's still in search of the dragon.
(The Dragon falls onto the medieval festive)
Computer: To order a parachute, please call our help desk. Self-destruct in 3, 2, 1.
(As the dragon self destructs, Candace runs into it. The resulting explosion sends Candace into the castle, then crashing back down the tower, only to be caught by Charles)
Candace: Hi, Charles.
Grandpa Fletcher: Jolly good, old bean.
Phineas: Ah! There you are, Perry.
Lawrence: Hello. we had the most amazing time. Look! I found this 19th century barometer. Anything interesting happen 'round here?
(There's silence for a moment)
Ferb: I hear there's a new version of Jane Eyre in the offing.

End Credits

(standalone broadcasts only)
(Song: "Perry the Platypus")
Male Singer: He's a semi-aquatic, egg-laying mammal of action
Backing scat: Dooby dooby doo-bah
Dooby dooby doo-bah
Male Singer: He's a furry little flatfoot, who'll never flinch from a fray........!
He's got more than just mad skill,
Female Singer: Wah-ah-ah
Male Singer: He's got a beaver tail and a bill
Female Singer: Ah-ah
Male Singer: And the women swoon whenever they hear him say:
(Perry chatters, women faint)
Male Singer: He's Perry! Perry the Platypus!