When Red and Gobo are getting ready to have a swim meet, the contest gets cut short when the Knobblies- thick, pink vines- come to the surface of the pond, leaving almost no room to swim. Boober brings some Kolerabi juice by for his friends to drink, but nobody likes it. But when Red dumps the juice on the vines, the vines shrink and die, giving more room in the pond. Boober then rushes back to make more so the swim race can still go on. When Red grabs one of the vines, they give her a vision, with weird creatures saying, "Follow the roots." Red then dives into the very bottom of the pond to find out where the message is coming from, and discovers that the vines are roots to a huge, underwater tree. When Red gets to the top of the tree, she finds five Merggles (mermaid Fraggles); Merboo, Merkey, Mermer, Merple, and Mervin. They are delighted that their message to Red worked, since they're now able to communicate with another species besides themselves. Meanwhile, back at the pond, Boober's Kolerabi juice is being dumped by the bucketload onto the Knobblies, and while Red's celebrating with the Merggles, the branches start dying, and they can't figure out why. Red then tells them of Boober's juice, and they lock Red in a cage, then swim far away before they die. But when Gobo grabs one of the vines up by the pond, he receives a vision to "Stop pouring the Kolerabi juice", and "Follow the Knobblies", which he does. It's up to Gobo to go find and rescue her before the tree dies and the Merggles leave forever.