6×07 Planet of the Ood: “I can’t do this anymore. I want to go home.” After learning Melody Pond’s true identity, Sammy demands that the Doctor take her home. But that’s easier said than done: as soon as they arrive back on Earth, the TARDIS is commandeered by none other than the Doctor’s former companion Harmony Beck. The Doctor doesn’t even have time to ask how Harm ended up on twenty-first century Earth before she’s sent them thousands of years into the future, where they will learn of the terrible secrets on the planet Oodsphere.