Doctor Who and the Android Invasion

When the TARDIS materialises just outside a sleepy English village, it appears the Doctor and Sarah Jane are nearly "home" at last. But all is not as it seems in rural paradise. White-suited, gun-wielding guards stalk the countryside, while the village itself is eerily deserted. As the Doctor and Sarah look on, a UNIT member leaps over a cliff to his death and, as the clock strikes twelve, the local pub is suddenly filled with strange robotic villagers. The UNIT member is amongst them, very much alive. What exactly is happening here?The Doctor is mystified, setting off for UNIT HQ in search of answers. There, with the Brigadier away, Senior Defence Astronaut Guy Crayford holds court. But just who is his shadowy master, the Thraal, Styggron? Indeed, who are the Thraals and what have they got in store for the Earth? Why has the TARDIS dematerialised seemingly of its own accord?The Doctor must move quickly to find the truth, for the very future of mankind hangs in the balance...