Kip. 27: A Touch-and-Go Situation! Gohan, Protect the Four-Star Ball!

27

Krillin surrenders his Dragon Ball to Vegeta after Zarbon is killed, knowing he doesn't stand a chance against Vegeta. While returning to his stashed Dragon Balls, Vegeta senses Gohan. Gohan also senses Vegeta, so he masks his ki and hides his newly found Dragon Ball. Vegeta eventually coaxes Gohan out but doesn't see the hidden Dragon Ball. Thinking he has all seven Dragon Balls, Vegeta lets Gohan live and takes off, after delivering a knee to his stomach. After returning to the nearby Namekian lake, Vegeta realizes Gohan had taken his hidden Dragon Ball and goes berserk. Meanwhile, Frieza is informed that the Ginyu Force, an elite fighting team, will be arriving shortly, bringing much needed state-of-the art scouters as well as extensive fighting strength. Goku continues his training at intense gravity levels within his spaceship. (Source: Wikipedia)