Hercule to the Rescue (地球軍、最後の秘密兵器！！ Chikyūgun, Saigo no Himitsu Heiki!!, lit. "The Earth Army's Final Secret Weapon!!") is the fortieth volume of the original Dragon Ball manga series. It is released in North America as Dragon Ball Z volume twenty-four, with the chapter count restarting back to one.
Breaking free from his master Bobbidi, the rampaging Boo turns the entire world into his candy store. To fight back, Goku transforms into his strongest form yet, the Super Saiyan 3. But the world's only hope may lie in Trunks and Goten, the world's youngest and most promising fighters. Using an alien fusion technique, they attempt to merge to form a single, even more powerful hero, Gotenks. Meanwhile, as Boo destroys city after city, the people of Earth call forth their secret weapon, the seemingly invincible (but actually incompetent) Hercule.
|"Goku Meets Boo!"|
Goku begins teaching the Fusion Technique to the boys. In order to buy time for Trunks to get the dragon radar, Goku has a confrontation with Boo.
|"Super Saiyan Level 3!!!"|
Goku shows Djinn Boo the powers of the saiyan race, unveiling, to the shock of everyone, Super Saiyan Level 3! The powered up Goku commences in battle with Djinn Boo!
The intense battle between Boo and Goku rages on! The powerful Djinn proves a worthy adversary for even Goku! Goku eventually ends the battle, and tells Boo that he will have a strong opponent. Boo kills Bobbidi.
Trunks returns with the radar.Goku says that Level 3 drains a lot of power, and took away some of the time he had left. Goku and Piccolo begin teaching the fusion to the boys.
|"Goku Goes Back"|
The fusion training continues, and Goku must return to the Other World.
|"Where is Gohan?"|
Goku searches for Gohan in the Other World. On Earth, Boo has met a young blind boy, who does not fear him. Goku learns that Gohan has been with the Lord of the Worlds.
|"The Zeta Sword"|
While training, Gohan breaks the Zeta Sword with Katchin. From inside, comes the Lord of Lords! He promises that he possess great power. Goten and Trunks further their training to become one mighty being!
|"The Fusion Succeeds...?!"|
Goten and Trunks fuse, but the first two times fail. Third time's the charm! Gotenks (battle only shown in anime filler) gets beat by Boo.
|"The Earth's Secret Weapon!"|
Hercule confronts Djinn Boo. This is the start of their friendship!
Goten and Trunks fuse as Super Saiyans, and form Gotenks. He wastes the whole thirty minutes, and the fusion splits right before they confront Djinn Boo.
|"The Friends of the Djinn"|
Boo finds and befriends a lost dog, which was hurt, until Boo healed it. The dog is shot by two men.
|"The Creature of Wrath"|
Boo is angry! Hercule attacks the two men. Later, Hercule is shot by the two men. This causes Buu to become angry and split into two Djinn Boos: the good and the bad.
The good Boo battles the bad Djinn Boo. The evil seems to be conquering the light, and as the good Boo tries to turn his bad counterpart into candy, it backfires! The evil Boo eats the Good, increasing his power by unimaginable means!
|Volume 40: Hercule to the Rescue|
|Goku Meets Boo! · Super Saiyan Level 3!!! · Boo Unbound! · Goku's Time · Goku Goes Back · Where is Gohan? · The Zeta Sword · The Fusion Succeeds...?! · The Earth's Secret Weapon! · Super Fusion! · The Friends of the Djinn · The Creature of Wrath · Two Boos?!|