Jo is shopping one day when she sees a spaceship land — right in the middle of London. Two blobby aliens approach her and seem to know who she is. As she tries to communicate, she has trouble saying certain words. Sergeant Osgood is left in charge of UNIT HQ, and notes an alien invasion. As he tries to inform the Doctor, the two of them also have trouble communicating. The Doctor notices that they can only say words using the vowel "o", and, as Osgood notes, sometimes "y".