VISITING THE HUMAN COLONY MENDORAX DELLORA, the Doctor is reunited with River Song. She fails to recognise his latest incarnation, instead mistaking him for the surgeon she’s summoned to operate on her near-dead husband, King Hydroflax. River explains that Hydroflax has the priceless Halassi Androvar diamond lodged in his brain and her real objective, rather than saving him, is acquiring the diamond. She instructs the Doctor to remove Hydroflax’s head.