Up early one morning, Sarah Jane is astonished to see that the house opposite hers has changed overnight: what used to be a nondescript 1970s family home has been replaced by a smart Victorian residence. How did a house from 1884 suddenly materialise in Bannerman Road? Where has the old O'Brien place gone? And more importantly, who – or what – has caused this temporal anomaly? Sarah Jane and friends must find out before time itself explodes and destroys the world...