(this image appears for illustrative purposes only and no attempt is made to supersede any copyright attributed to it)
A yellow robot was sent to Earth to find the heir to the throne of its planet.
Along with a red robot, it removed all the humans, apart from Clyde Langer and Rani Chandra who were "grounded" by the Judoon, from Earth while they searched. The heir, a half-human called Gavin, was hidden by a bio damper. When removed, the robots recognised him. They returned the humans and took Gavin home.