The Doctor, Romana, and K9 arrive on an uninhabited planet made entirely of confectionery. K9 seems in a bad mood, and Romana realises it is K9's birthday. To celebrate the occasion, she takes the Doctor's TARDIS to Barastabon to fetch a dedicated sponge cake from the Masterbakers of Barastabon. After a brief time storm-induced detour to the planet Kendrax during which she ably foils an alliance of the Master, the Daleks and the Cybermen, she returns with the Cake.