Lana springs into action when she learns her favorite fish are in jeopardy of losing their home to construction.
Lana is hanging out with her favorite fish at Tall Timbers Park, the Fishmans, who also have happened to lay hundreds of eggs. As she plays with them, a bulldozer suddenly arrives. When Lana asks the bulldozer driver what the big deal is, he states that the park had been sold and is going to be the location of a new Mustard Warehouse. Realizing the danger the Fishmans are in, Lana has Hops secretly dismantle the bulldozer, prompting the driver to leave so he can get the tools to fix it.
Heading home, Lana learns from Rita and Lynn Sr. that in order for her to save the Fishmans from getting killed, she has to get people to sign a petition. However, when she needs to collect 10,000 signatures, and the petition doesn't actually stop the construction of the warehouse (but instead delays the construction), Lana decides to go an easier route by disguising herself as a lake monster (after Leni mistook Lana for a monster due to being covered completely in mud). Recruiting the animals, Lana, Hops, and the animals successfully scare off the construction worker from the day before to stop him from doing any damage by posing as a menacing swamp monster, but not before taking a screenshot of the "monster" he's seeing. With the construction worker gone, Lana believes she has successfully saved the Fishmans.
Sometime later, Lana arrives back home and learns from the news that because of the construction worker's sighting of a "monster", the construction of the Mustard Warehouse will be relocated, much to Lana's joy. Unfortunately, when Lana heads back to the lake the next day, she's shocked to discover dozens of people surrounding the lake, waiting for the monster to reappear. Clearly annoyed at this turn of events, Lana and the animals bring out their monster disguise and scare a bunch of people at a different park. Although the plan succeeds in getting rid of everyone at Tall Timbers Park, karma rears its ugly head when it is revealed that the park Lana just scared a bunch of people at was going to be the new location of the Mustard Warehouse, but because of the "monster's" new sighting, construction at Tall Timbers has resumed. Realizing that she can't do the same stunt again, Lana eventually goes the hard route by trying to collect 10,000 signatures. Despite her efforts, Lana barely manages to make 10,000 signatures and admits defeat. Suddenly, Lisa discovers one of Lana's photos of her with the Fishmans, and realizes that the Fishmans are an endangered species of sturgeon, and are therefore protected by law.
With the lake now protected from any construction, Lana is happy to know that the Fishmans can raise their babies without any harm whatsoever.