DRAGONBALL Z MOVIE 7: SUPER ANDROID 13

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.

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. Not wanting to destroy the city they're in, Goku and Future Trunks, who had arrived just then, leave for an uninhabited Arctic area. The fight seems even until Android 13 shows up - at least until Vegeta and Piccolo arrive. At that point of time, both Goku, Vegeta, and Trunks ascend to their Super Saiyan forms and 14 and 15 are destroyed by Trunks and Vegeta, respectively. Just when the fight seems won, 13 shows off his "Super" form by absorbing two components of the two fallen Androids, transforming into a blue behemoth and vastly increasing his power, changing the battle's outcome yet again. Despite all their efforts, Goku, Vegeta, Piccolo and Trunks are subsequently beaten by the powerful android. But then Goku prepares his Spirit Bomb, and, after transforming into a Super Saiyan, he absorbs its energy into his body (Krillin remarks that Goku's ability to transform shows that he retains his pure heart in Super Saiyan form) and destroys the Android menace. As 13, 14, and 15 are ultimately destroyed, Dr. Gero's computer shuts down for good, while still shouting the words "Goku must die!". The film closes Goku and his friends healing in the hospital.

Source: http://en.wikipedia.org/wiki/Dragon_Ball_Z:_Super_Android_13!