Tick and Arthur are at a flower show when American Maid shows up to view a rare 400 year old bloom. They meet with Professor Ichibana, its guardian, who warns that 800 years old they had a "bad bloom." Ichibana warns a crazed villain has been following them – El Seed. Nearby, El Seed fires a plant seed which grows into a giant attack plant. Tick and Maid fight them off while Arthur goes with Ichibana, who gives him the bloom for safekeeping but warns he must keep playing music, then flees after trading with Arthur's plant. When his plants are defeated, El Seed calls in his Bee Girls to help him.
The music runs out as the heroes are in their taxi and the plant starts to bloom. American Maid manages to come up with singing "America the Beautiful," which calms it for the moment. El Seed has captured Ichibana but doesn't heed her warnings about the bloom and sends the Bee Girls after the heroes. At their apartment, Tick and Arthur have found a radio to provide music, but are briefly interrupted by a newscast about Ichibana's capture. Maid and Tick go off to look for the professor but the Bee Girls have found Arthur and send in an attack plant-monster, Rosebud. It defeats Arthur and takes the 400-yeer old bloom back to El Seed. El Seed leaves a plant to kill her then departs.
Tick and Maid are searching the city and spot "La Fleur" Hotel, then hear Ichibana yelling for help. They free her and defeat the plant and Ichibana brings them up to speed. They check up on Arthur, who lets them know El Seed has the bloom. At the City Botanical Gardens, El Seed turns off the music and the 400-year old bloom begins to…bloom. The heroes use Arthur's hay fever to track the bloom and they find its location just as it grows to huge size and breaks through the roof. The Human Bullet responds to the crisis but his son is unavailable and he needs his neighbor to fire him when his wife refuses.
The bloom has grabbed El Seed while the heroes try to stop the ever-growing bloom. American Maid tries to grab El Seed but is knocked clear by the Human Bullet. The Tick begins singing opera but Rosebud and the Bee Girls attack. Arthur manages to defeat the Bee Girls by sneezing so they hit each other, and Tick signs loud enough to blast Rosebud unconscious. He continues to shoot but El Seed shots plants into his mouth and the Tick starts spewing plants out of his mouth. Arthur sings to calm the bloom while Tick spits a seed at El Seed, knocking him out. Afterward, the heroes look on in triumph as El Seed and his gang are taken to jail.