In a different timeline.........Goku has suffered a heart attack and has died, not long after that, Androids #17 and #18 arrives. The Z fighters go to try to stop the Androids, but without the help of Goku, they were no match for the Androids' power. Yamch, Tien, Krillin, Piccolo, and Vegeta were all killed by the Androids. There are only two people left who can stop the Androids, Gohan and Trunks.
About 13 years later........The Androids have taken control over earth and they are destroying people and cities. Trunks is riding in a car with his mom, Bulma,Trunks hears over the radio that the Androids are destroying another city not too far from where he is. Trunks goes to put an end to the terror, but when he arrives, the Androids have already destroyed the city and have left. Trunks then runs into Gohan and asks Gohan why the Androids are doing this, Trunks then tells gohan that he wants to stop them and would like for Gohan to train him. Gohan starts to train Trunks just like Piccolo trained him. Gohan and Trunks go to do battle with the Androids, but they quickly find out that they are not strong enough to defeat them, Gohan tries to to hide Trunks and himself from the Androids, but the Androids shoot a big blast and destroys the area, hoping to kill Gohan and Trunks. Because of the blast, Gohan has lost an arm, Gohan see's Trunks lying on the ground. Gohan reaches to get a sinzu bean , but there is only one left, so he gives it to Trunks and he faints. Trunks carries Gohan to Bulma and tells Bulma that Gohan saved his life. After Gohan has healed, he continues to train Trunks, Trunks keeps trying to become a super saiya-jin, but he can't. All of a sudden, Gohan and Trunks see an explosion and know that it must be the Androids destroying another town. Gohan gets mad and goes super saiya-jin, Trunks wants to help Gohan , but Gohan doesn't want Trunks to get hurt. Trunks tells Gohan that he didn't train this hard just to sit around and watch, Gohan tells Trunks to get ready to fight and then Gohan hits Trunks in the back of the neck and knocks him out. Gohan then goes to fight both Androids by himself, even with only one arm, Gohan puts up a good fight, but then Android #18 joins the fight and they finally end up killing Gohan. Trunks wakes up after the fight, but he can't feel Gohan's ki, he races off to the battles site and finds Gohan lying on the ground dead, this gets Trunks really mad and Trunks finally turns into a super saiya-jin.
Three years later...........Trunks thinks that he is now strong enough to defeat the Androids and goes to fight them. Trunks goes super saiya-jin and starts to battle the Androids, but he quickly finds out that he is not strong enough yet and the Androids beat him up and leave him for dead. Bulma finds Trunks and nurses him back to health, Bulma tells Trunks that none of this would of happened if Goku hadn't of died from a heart attack. After Trunks has healed from the fight with the Androids, Bulma gives him some heart medicine for Trunks to give to Goku. Trunks gets into the time machine and goes back in time to save Goku...............and a new battle awaits him!
