In the beginning, Six and Four are going to play with what looks like a seesaw when Six begins to act strange. As it turns out, Six has the dreaded lurgi, which ends up spreading to Four.
The alarm sounds. Agent 58 is calling in to report a boy on a trampoline who can't stop jumping. Five goes out to solve the problem, while Three mans the Control Room.
Once Three finds a number for Five to land on, the sick male Numberjacks go for a lie down.
More problems arise when a man in a café, a cook, and a boy on a bouncy castle find themselves unable to stop jumping. Five discovered they've been blobbed! It's (gulp) the Problem Blob, back up to his old tricks!
Three fires up the Brain Gain machine, and her and Five sort out the people going up and down. But the problems aren't over yet; now people can't stop going round and round!
Five is ready to solve more problems, but Three isn't. She's got the lurgi too! Five worries about what could happen (cue Imagine Spot), like people in a lift (elevator) going up and down nonstop!
Five and Three remain persistent, even when things get even crazier when people start going up and down and round and round! With the Agents' help, Three manages to make enough Brain Gain to set everything straight.
Five returns to the sofa, and Three goes to join her sick friends. Five and the Agents recap the episode.
Finally, Five visits her sick friends, who are feeling much better. Four is worried that Zero has the illness, but Five assures him he's just behaving like his usual self. All is well in the Numberjack sofa once more.
This episode provides examples of:
- Big Sister Instinct: Five acts very sisterly in this episode; first, she takes over watching the screens for Four, who is sick, then guides Three through the control room when she's left on her own.
- Chuck Cunningham Syndrome: Aside from "Seaside Adventure", this was the last appearance of the Problem Blob.
- Dwindling Party: Six is first to go, then Four, and then Three. By the end, only Five is left out of the main four.
- Five-Second Foreshadowing: Four makes gestures related to the symptoms Six lists before it's revealed he also has the lurgi.
- Sick Episode: Six, Four, and eventually Three are infected with lurgi, which causes a "hurty head, achy body, horrible all over" feeling.
- Stock Shout-Outs: "The Lurgi" is a common Brittish slang for "The Virus," originating from an episode of The Goon Show (funny enough, the episode "The Dreaded Lurgi.")
- Tempting Fate: At the beginning of the episode, Three says she hopes she doesn't catch the dreaded lurgi. Guess what happens just as the problem for the episode gets worse.
