Deep in a hidden laboratory, Bio-Broly and a crew of humanoid specimens awaken from tanks after being created by the scientist Professor Collie, under the watchful eye of the scheming employer Mr. Jaguar. Jaguar’s plan is to weaponize these bio-warriors to expose the world’s greatest fraud, all while a muscular, tail-bearing figure lies dormant in another tank, hinting at a far darker secret waiting to be played out.
Android 18 hounds Mr. Satan for payment after their bout at the World Martial Arts Tournament, and a businessman named Men Men arrives with a blunt warning: Jaguar has invited Mr. Satan to his island laboratory to fight his elite fighters, and refusal could expose him as a bed wetter. Reluctantly, Mr. Satan agrees to go, with Android 18 along to ensure the bargain sticks, while Trunks and Goten slip away in search of a true challenge.
On the island, a brutal tournament is staged to pit Jaguar’s bio-warriors against Mr. Satan. Android 18, Goten and Trunks join the mix by posing as his students, and the young Saiyans quickly show their edge by dispatching the bio-warriors. Their exploration leads them to a tank that houses Broly, believed dead, and they confront a shaman who reveals a shocking secret: after Broly’s supposed death, Jaguar obtained a sample of the Legendary Super Saiyan’s blood and used it to create a clone. Although Goten and Trunks try to destroy the clone, it bursts free and attacks them, triggering a catastrophic leak of a dangerous bio-fluid that devours matter on contact.
The Bio-Broly clone is swept up and deformed by the fluid, but remains alive. Jaguar orders Bio-Broly to kill Mr. Satan, but Android 18 intervenes and is eventually defeated as the chaos spirals. Goten and Trunks take on Bio-Broly while the bio-fluid wipes out the bio-warriors, scientists, and the shaman alike. Bio-Broly overwhelms Goten, Trunks, and Android 18, and Krillin arrives to help, saving Android 18 but falling in the ensuing clash.
In a desperate gambit, Trunks lures Bio-Broly beneath a bio-fluid containment tank and detonates it, blasting Bio-Broly with more fluid. The creature appears to dissolve, but secretly merges with the liquid and briefly re-emerges as a colossal head before vanishing again. The survivors realize the bio-fluid will continue to spread unless it is halted. They discover that seawater solidifies the fluid, so Goten, Trunks, and Krillin unleash a combined Kamehameha at the island’s base, sending a massive wave of seawater that floods the facility and turns the fluid to stone. A gigantic Bio-Broly rises from the sea only to solidify, and the trio finishes him with a final Kamehameha—destroying the threat for good.
Meanwhile, in the Other World, Goku receives orders from King Kai to join Pikkon in stopping Broly, who has been granted a physical form and is rampaging through Hell.
