The Doctor (David Tennant) and Donna (Catherine Tate) land on a planet called the Ood-Sphere in the year 4126, where a company called Ood Operations has been harvesting and selling the Ood as servants. A number of people have been killed lately. The CEO of Ood Operations, Klineman Halpen (Tim McInnerny) tells the Doctor all the victims have been electrocuted by the Ood’s translating spheres.

Donna feels sympathy for the Ood and is horrified by their enslavement. The Doctor believes no species could naturally evolve to be servants. He and Donna find a batch of uncultivated Ood singing together. Instead of translation spheres, they hold a hindbrain which gives them individuality. The hindbrain is removed and replaced by the translation sphere by the humans to make them subservient.

The Doctor accuses Halpern of performing lobotomies. He and Donna are captured by company security. Soon the Ood begin a mass revolution and an evacuation is begun, but nearly everyone is slaughtered. The Doctor and Donna escape with the help of the Ood, after they are convinced to resist their brainwashing, and follow Halpen to a locked warehouse containing a giant brain that is the collective consciousness of the Ood.

The brain’s control of the Ood is limited by a forcefield within a circle of pylons. Halpen plans to kill the brain and all the Ood and start over, but is stopped by the Doctor, Donna, and Doctor Ryder (Adrian Rawlins). Doctor Ryder is an activist for Friends of the Ood and has lowered the forcefield. Halpen is outraged and throws Ryder into the brain, killing him. Halpen’s servant, Ood Sigma, has been using Halpen’s hair-loss medication to slowly convert Halpen to a Ood, which happens suddenly in a rather horrifying scene. He tells the Doctor and Donna that he will take care of his befuddled former master. The Doctor shuts down the pylons and frees the Ood. They sing in a telepathic collective. Ood Sigma promises to create an Ood-song in honour of Doctor-Donna.

The Ood-sphere is related to the nearby Sense-sphere that the First Doctor encountered in the 1964 episode The Sensorites. Planet of the Ood was favorably reviewed, particularly Donna Noble’s passionate role. The Oods’ eyes glow red when they are being manipulated, like the Robots of Death visited by Fourth Doctor Tom Baker. Tim McInnerny played comic roles in Blackadder, but here he is a raving villain. Watching him turn into an Ood is satisfying, but they had to tone down the horror of the transformation so as not to scare the kiddies. The snow scenes were filmed on a blazing hot August day with bits of paper as snow. The Ood songs were haunting, performed by an amazing tenor named Mark Chambers.