"A day without Ferb Fletcher, delete a brother."

The episode begins on a normal summer's day with Phineas & Ferb and their pet platypus sitting under their tree in their backyard. Suddenly, a time glitch happens, and Ferb disappears.

Phineas: "Ferb! Ferb!"

We see Phineas run into the house, similar to how Candace got upset in the episode "Last Day of Summer," hugging her mum.

Phineas: "Mum, have you seen Ferb?"

Mum: "Phineas, I'm sure it's going to be okay, honey, but who's Ferb?"

Phineas blinks and gets confused.

We zoom into Perry the Platypus in the backyard who's sleeping on the grass near the tree. The beep of Perry's watch goes off. Perry falls down the grass.

Major Monogram: "Good morning, Agent P! We've got a serious mission for you! Listen up, Agent."

Perry the Platypus keeps falling asleep.

Major Monogram: "Agent P, this is no sleeping matter."

Agent P wakes up.

Major Monogram: "It's Doofenshmirtz again. This morning, Doofenshmirtz fired a strange inator from his building. We need you to get over there and find out what it is. There are random people disappearing in the tri-state area. Get over there, Agent P."

We hear Perry's theme song.

Perry reaches Doofenshmirtz Evil Inc. We get the classic jingle that says Doofenshmirtz Evil Inc.

Perry has landed on his jet pack outside of Doofenshmirtz's window and hears Doofenshmirtz's inator firing.

Doofenshmirtz has a trap set for Perry the Platypus. We hear Doofenshmirtz say, "Hello, I know you're there, Perry the Platypus." A large rope is tied to Perry's foot, dragging him hanging upside down in front of Doofenshmirtz.

Doofenshmirtz: "You know, that was kinda rude, Perry the Platypus. You could have just walked in."

Perry points at the traps Doofenshmirtz set.

Doofenshmirtz: "Oh, right."

Doofenshmirtz: "Well, Perry the Platypus, you're probably wondering why you hear me firing my inator randomly across Danville, right?"

Doofenshmirtz: "Well, I'll tell you. So, it never occurred to me before, why not shoot every sibling in the tri-state area, including my brother Roger, and take over the tri-state area."

Doofenshmirtz: "Don't look at me that way, Perry the Platypus. To be honest, shooting other siblings' brothers is just an extra bit of extra evil. Haha. Anyway, behold, Perry the Platypus, my Make Siblings Disappear Inator. With one shot of this, I'll make my brother Roger disappear like he never existed and rule the entire tri-state area! Hahaha."

We pan back to Phineas and Ferb's backyard. We see how this affects Phineas that Ferb's gone.

Phineas: "Ferb, where are you?" Sits by the tree, the boys make plans for their inventions.

Isabella walks in.

Phineas: "Hey, Phineas, what are you doing?"

She smiles at Phineas.

Phineas: "Hey, Isabella, I'm about to figure out how I'm going to find Ferb! He randomly disappeared, and I don't know where he is. Maybe he used one of our inventions to teleport by mistake or something. That's got to be the case."

Isabella: "Phineas, I'm sure it's going to be okay. But who's Ferb?"

Phineas: "Ferb's my step-brother; we build everything together. Isabella, you know Ferb, so does Buford and Baljeet. Stop joking with me."

Buford, Baljeet: "Who?"

Phineas gets upset and runs out of the backyard. We have Phineas saying to himself.

Phineas: "How do I remember Ferb, and nobody else does?" We get this sad song sung by Phineas.

Today I'm walking down Danville, it doesn't feel right,

There's no Ferb by my side, in the day or night.

Everyone thinks Ferb doesn't exist, it's a curious plight,

Every time I ask, heads nod, and I'm filled with fright.

Oh, where is my step-brother Ferb?

Someone pinch me, I think I've hopped into another dimension.

Ferb, oh Ferb, where did you go?

Invisible like a ghost, you've left me in woe.

Phineas is confused, his heart filled with dread,

Hoping you'll come back, wipe away tears he's shed.

Every corner of the town, I'm searching all around,

For my buddy Ferb, but he cannot be found.

Phineas is lost, his heart's filled with fears,

Hoping Ferb will reappear, wiping away his tears.

Oh, where is my step-brother Ferb?

Someone pinch me, I think I've hopped into another dimension.

Ferb, oh Ferb, where did you go?

Invisible like a ghost, you've left me in woe.

Phineas is confused, his heart filled with dread,

Hoping you'll come back, wipe away tears he's shed.

Did you venture to a world beyond our sight?

Or fade into the shadows, like the sun at night?

I'll keep on searching, through the day and night,

Hoping one day, you'll be back in my sight.

Ferb, oh Ferb, where did you go?

Invisible like a ghost, you've left me in woe.

Phineas is confused, his heart filled with dread,

Hoping you'll come back, wipe away tears he's shed.

Ferb, oh Ferb, wherever you may be,

Know that you are missed, come back to me.

Together we'll face this mystery, no more fears,

Phineas and Ferb, through laughter and tears.

We pan back to Doof where Doof is on the top of his building with Perry the Platypus still trapped.

Doof: "Well, the moment has come, Perry the Platypus, to delete my brother outta existence. Did I mention the inator only hits one sibling, and it's always the younger sibling, or the step-brother or something to the other sibling? Ehh, I guess it doesn't matter anyway, Perry the Platypus. Now to hit my younger brother Roger with my inator." And fire.

Perry comes outta nowhere, jumping on Doofenshmirtz.

Before Perry destroys the inator, we see him press the reverse button. Before Perry gets his hover jet and jumps onto it, driving it back to Phineas and Ferb's backyard.

We hear Doof say, "Curse you, Perry the Platypus!" from his building!

Perry sees Phineas upset.

The inator reverses everything.

Phineas is crying over a pic of Ferb, remembering his memories with Ferb.

Ferb randomly appears.

Ferb: "Okay, what did I miss?"

Phineas: "Ferb!" (Phineas hugs Ferb.)

Ferb: "Was I just a ghost?"

Phineas: "Uh, yes, yes, you were."

Phineas: "Anyway, Ferb, I'm glad to have you back."

Phineas: "Oh, there you are, Perry. Look, Ferb's back!"

Perry: "Grrr."

Phineas & Ferb's Mum: "Who wants pie?"

Phineas: "Me, please."

We see Ferb walk into the house with Perry, and Phineas looks at the audience.

Phineas: "I have no idea what happened." (Blinks at the camera. Episode comes to an end.)