The Unbeatable Enemy Within! Goku vs. Android 19! (Attacked on Both Sides by an Internal Enemy?! Son Goku vs Artificial Human #19) is the sixtieth episode of Dragon Ball Z Kai. The episode first aired in Japan on June 6, 2010. Its American air date was March 9, 2011.
As Goku, Piccolo and Tien Shinhan take the Red Ribbon Androids to a new location to battle, Krillin revives Yamcha with a Senzu Bean. However, once Yamcha reveals the androids' ability to absorb energy, Yamcha, Krillin and Gohan head off to warn the others.
Meanwhile, it is revealed to Goku that the androids are a result of years of research conducted by Dr. Gero, in which miniature spy robots were used to analyze Goku's fighting techniques and developments in strength, all in an attempt to exact revenge on Goku for destroying the Red Ribbon Army. However, Gero did not analyze Goku during his time on the planet Namek, and thus the androids are unaware of his ability to transform into a Super Saiyan, which Goku gladly demonstrates in front of them.
A battle then ensues between Super Saiyan Goku and Android 19. Though Goku seems to have the upper hand, he soon appears to be losing energy, especially once Android 19 absorbs the energy from Goku's Kamehameha. Eventually, Goku is seen clutching the left side of his chest, which Gohan immediately recognizes as a symptom of the heart virus which was predicted by Future Trunks. Gohan then reveals that Goku never became sick from the heart virus in the last three years so he was not treated with the Heart Medicine, but the virus seems to be affecting him now, six months after what Future Trunks had predicted. As Goku struggles to stay conscious, Android 19 prepares to finish the battle by absorbing Goku's remaining energy. Piccolo tries to intervene, but Android 20 blasts Piccolo with his eye beams, which sends him crashing to the ground.