Phineas: Candace, it's your turn to clean up the living room today!
Candace: But... I-I did last yesterday! Yeah, I did that!
Phineas: Come on, Candace...
Candace: Ha! You can't prove that it's my turn, because Mom and Dad was away yesterday.
Phineas: (turns around to Ferb) Ferb, I know what we're gonna do today! We're gonna build... a lie-detector!
Phineas and Ferb starts to work on the lie-detector, when Buford, Baljeet and Isabella arrives.
Isabella: Hi Phineas Hi Ferb! Watcha doin'?
Phineas: Today, we are building a lie-detector!
Isabella: Really? That's so cool!
Phineas: Hey, where's Perry?
Perry is inside the house. He presses a button hidden in the Camel-lamp. An underground passage opens and Perry climbs down.
Carl: Ahh, Agent P! Major Monogram is sick today, so I'm giving orders today! Ahem! Dr. Doofenshmirtz has bought something from a petshop, find out what he bought and find out why!
Perry makes salutes and runs off.
Phineas: Now it's done!
Baljeet: Who will test it out first?
Everyone looks at Baljeet
Baljeet: Why do I have to test it first? Maybe it will erase my brain!
Phineas: Relax, it's harmless!
Baljeet: Oh well...
Baljeet walks over the machine and sits down on a chair. Ferb puts a helmet on Baljeet.
Phineas: Okay, we are gonna ask you a question, and if what you say is true, this lamp will be green, but if you lie, the lamp will get red. Understood?
Baljeet: Okay, ask away!
Phineas: Hmm... do you think you're smart?
Baljeet: Well, yes, yes I do.
The lamp flashes green
Isabella: Who is your crush?
Baljeet: WHAT? Uhh... no one..
The lamp flashes red
Buford: Are you a nerd, nerd?
The lamp flashes green
Phineas: Well, the lie-detector works perfectly! Now, let's test Candace.
Perry knocks on Doofenshmirtz door.
Doofenshmirtz: Ohh, Perry the Platypus! Come in, come in, don't be shy!
Doofenshmirtz: You maybe wonder what I'm up to, hmm? Well, it has nothing to do with the petshop, as Carl told you... eheheh...
Perry glares at Doofenshmirtz.
Doofenshmirtz: Well, I guess I have to trap you.
Doofenshmirtz picks up a remote and presses a button so a cage falls down on Perry.
Doofenshmirtz: Aww, I thought you would fall for the petshop thingy. By the way, I just went in there to look at the animals... Well, now it's time for my evil plan! I installed spy-cameras all over the O.W.C.A-lair! So I could see you get your mission! Yes, Perry the Platypus, if I show people this video, O.W.C.A is gonna close, because it's top secret, and then you won't be an agent anymore, and then... then I can take over the Tri-State-Area!! AHAHAHAHAHA!
Phineas walks into the house
Candace: (talks to Stacy throught her cell-phone) And I was like, oh no you didn't, and she was like, oh yes I did, and I was like...
Phineas: Candace! Come, look what we've made!
Candace: Sorry, Stacy. My goofy brothers are up to something again. C.Y.A B.F.F!
Candace: This better be good.
Phineas: Come and look!
Candace followes Phineas and Ferb to the backyard.
Candace: What is...that?
Ferb: It is a lie-detector that reveals if you are a lier or not.
Phineas: Wanna give it a try?
Candace: Oh no, no way I'm gonna test that...thing! It could erase my brain!
Baljeet: Told ya'.
Ferb: Also, another good lie-detector is that if you don't wanna test it, it means that you hide something.
Candace: No, I don't... but... I... Fine: Test me!
Candace sits down on the lie-detector chair grumpy. Ferb puts on the helmet.
Phineas: Okay, do you like us?
Candace: You and Ferb? You're my brothers, duh. I like you like a sister likes a brother.
Light flashes green
Phineas: Okay... now for the real thing... did you clean he living room yesterday?
Candace: I... I d-did it... y-yesterday...
Light flashes red
Candace: Don't say a word!
Candace leaves and goes to the living room and starts grumpy to clean the living room.
Doofenshmirtz takes another remote from a shelf.
Doofenshmirtz: See this, Perry the Platypus? Yes, with this remote, I can controll the spy-camera! If I press this button, all the cameras will be POOF! Gone! Oops.. Maybe I should not tell you that...
Perry liftes the cage and is free.
Doofenshmirtz: Aww, man! I knew I should have bought that heavy cage...
Perry snatches the remote from Doofenshmirtz hand and presses the button that makes the cameras disappear.
Doofenshmirtz takes a third remote from the shelf.
Doofenshmirtz: Taste this! AHAHAHA!
Doofenshmirtz shoots lazer with the remote.
Phineas: How about you, Isabella, do you wanna try?
Isabella sits on the chair and Fer puts on the helmet.
Isabella: Ready spaghetti!
Phineas: Okay... hmm... do you think that I am a nice guy?
Isabella thinks to herself: This is your chance, Isabella! Today I'm gonna tell Phineas the truth!
Isabella: Yeah, but you are more than that. I lov--
A beam of lazer from Doofenshmirtz remote hits the lie-detector.
Phineas: ISABELLA! WATCH OUT!
Buford: Oh man, it's gonna explode!
The lie-detector explodes. BOOM!
Phineas runs to Isabella that lies on the ground.
Phineas: Isabella? Isabella?!
Isabella: I'm okay... but it feels like my brain got erased!
Baljeet: I told you, I told you!
Isabella: No, Baljeet, I mean that I am chocked...
Baljeet: ... oh.
Perry snatches the remote from Doofenshmirtz hand and shoots all the other remotes and then he throws the remote from the building.
Doofenshmirtz: NOOO! CURSE YOU, PERRY THE PLATYPUS!
Perry jetpacks away from Doofenshmirtz, heading home.
Phineas: Oh, there you are, Perry!