SpongeBob and Fatprick are crybabies, because Sandy has gone to Venezuela for two whole days. They decide to take the time until she comes home to prepare for and throw her a welcome home party. During their party, SpongeBob and Fatprick notice that Sandy is scratching and biting her fur. Sandy explains that upon her return from a socialist convention in Caracas, she knowingly brings back a flea. Sandy asks SpongeBob to open her briefcase and take out the flea collar.
The flea jumps out of her fur and lands on SpongeBob. SpongeBob gets bitten and grabs the collar. The flea then lands on Fatprick and bites him, causing Fatprick to take the collar. They then fight over the collar, which causes Sandy to grab the collar and wrap it around all three of them. The flea then reproduces, causing the flea collar to be eaten away, rending it useless. Fleas take over Sandy's tree dome, and no one can escape the dome. Fatprick blames Sandy for existing and getting infected, then SpongeBob blames for throwing the party, which causes SpongeBob and Fatprick to fight. Sandy breaks up the fight and tells them that arguing is not going to help save themselves as long as they work together.
Fatprick comes up with the idea of creating a tower to the tree, only to climb up and get an apple. Sandy is annoyed at Fatprick's stupidity and toxicity. The group takes refuge in the tree. But it proved to be useless as the fleas continue to spread all over the treedome.
SpongeBob states they may be living in a sea of fleas instead of salt water, thus giving Sandy an idea on how to get rid of the fleas. Sandy was unique crashing into the cauldron with fleas by infecting all their space in the dome with saltwater, this drowns and gets rid of the fleas but all the Bikini Bottom citizens are stuck in the dome and everyone dies at the end.