The film opens with Goku's death from a viral heart disease and the death of the Z-Fighters at the hands of Androids #17 and #18 six months later. The Z-Fighters are unable to be brought back to life because the Dragon Balls are permanently unusable due to Piccolo's death. The TV Special moves into the future where Trunks is 13 years old and 23-year old adult Gohan is the only one able to stand against the Androids, ever since he became a Super Saiyan after witnessing the deaths of the other Z-fighters. Gohan trains Trunks in fighting and power, who comes very close to becoming a Super Saiyan as well. One day, The Androids attack an amusement park, where Gohan and Trunks come to the aid of the people. #17 takes on Gohan while #18 sits back and watches. Gohan transforms into a Super Saiyan and, despite a few lucky hits by #17, quickly takes control of the fight.
However, #18 joins the fight and begins to beat Gohan. Trunks, though no match for the Androids, comes to the rescue and takes on #18. He manages to fight her for a minute before he is defeated, but Gohan saves him from death, and they both hide in the debris. #17 and #18, unable to find them, figure they left but blow the park up anyway. Gohan and Trunks survive the blast but at the cost of Gohan's left arm. Gohan recovers and resumes training Trunks. The training is stopped short when the androids attack the Capitol. Trunks wants to fight, but Gohan knocks him unconscious because he couldn't afford for Trunks to get hurt again like before. The one-armed Gohan ambushes #17, and despite his handicap, puts up a long and suspenseful fight against the androids, but meets his end when the androids knock him to the ground and shoot ki blasts like a machine gun from the sky. Trunks is awakened when Gohan's ki vanishes. Upon searching the city, Trunks finds Gohan's dead body. The rage from within him is unleashed and Trunks transforms into a Super Saiyan.
The story moves forwards three years later and Trunks is now 16 years old. While Bulma is working on the time machine, Trunks goes off to fight the Androids. Trunks barely puts up a fight and is eventually beaten by the merely-toying Androids. He miraculously survives a large blast of ki from Android #18. Trunks awakens in his house with his mother Bulma by his side. After a brief talk, he decides to go in the time machine (once it's finally ready, which is about six months to a single year later) to give the heart medicine to Goku.