Parenthood

"Parenthood" is the third episode in the ninth season of Doctor Who, set on Cabra in supossedly 6014. It sees the re-appearance of the Doctor's daughter Jenny.

Synopsis
"I look young enough to be your boyfriend!" - The Doctor

Needing to take care of family business, Billy returns to Earth for a little, while the Doctor receives a strange signal from a distant location. When he arrives he is reunited with his daughter Jenny, from The Doctor’s Daughter. But she needs his help, in building a TARDIS to take her to another planet, off the desolate earth-moon of Cabra. But the Sinistral Mandraga has other plans, and have used Jenny to lure the Doctor into a deadly trap.

Jenny and Cabra
After she regenerated in The Doctor’s Daughter, she took a ship and searched for the Doctor for a long time. She finally crashed on the mysterious planet of Cabra, and encountered the Sinistral Mandraga, a race of cloaked beings who seek the infinite knowledge of Time Lord, which Jenny does not say she is to avoid being “devoured” by the Mandraga. The Doctor receives a signal from her sent from Cabra, and arrives, reuniting with her. The Doctor has regenerated twice before, and Jenny comments that he looks young enough to be her brother. The Doctor is overjoyed in finding her again, but soon after the Sinistral Mandraga appears, and demands the Doctor’s mind. The Doctor and Jenny escape the Temple of Mandraga on Cabra, fleeing to the abandoned city of Kuth, where the Mandraga seek them out, sensing Jenny is also a Time Lord. The leader of the Mandraga, Kastreth, taunts the Doctor with his knowledge of the Time Lords and Time War, and says that the Mandraga fought also. The Doctor comes forward, apparently giving himself up, but flees again with Jenny and steals the Crystal of The Balance, which destroys Cabra if it leaves the planet. The Mandraga pursue the Doctor and Jenny as they flee back to the TARDIS, and as they leave Cabra burns and the Mandraga are destroyed. Jenny, having experienced another adventure with “her father”, seems eager for more, and asks if she can join him. The Doctor tells her about Billy, and that he already lost someone when he brought to many people with him. He tells Jenny that he will take a part of his TARDIS to construct one for her, and then leaves her on a distant planet with her own TARDIS, saying he will see her again.