The film opens with the introduction showing the death of Dr. Gero at the hands of the Androids 17 and 18, and also revealing that Gero is still around in the form of an underground computer, still working on three new Androids (Android 13, Android 14 and Android 15), the first of which being presumed as one of original ultimate androids.
The real film now opens with the completion of Androids 14 and 15, who attack Goku while he is shopping with Chi-Chi and Gohan at West City. Not wanting to destroy the city they are in, Goku and Future Trunks leave for an uninhabited arctic area. The fight seems even until Android 13 shows up; at least until Vegeta and Piccolo
At that point of time, Goku, Vegeta, and Trunks ascend to their Super Saiyan forms and Androids 14 and 15 are destroyed by Trunks and Vegeta, respectively. Just when the fight seems won, Android 13 shows off his "Super" form by absorbing two components of the two fallen androids, vastly transforming into a blue behemoth and increasing his power greatly, changing the battle's outcome yet again. But then Goku prepares a Spirit Bomb, and, after transforming into a Super Saiyan, he absorbs its energy into his body and destroys the Android menace in a style similar to that of his Dragon Fist technique. As Androids 13, 14, and 15 are ultimately destroyed, Dr. Gero's computer shuts down for good, while still shouting the words "Goku must die!”
Vegeta attacks Super Android 13
Added by Android TGS
At the end, it closes with a comic relief. Goku and his friends are healing in the hospital, but Piccolo and Vegeta are sitting back-to-back on a small rock in the sea, isolated from the celebration.