The Doctor is back in the lives of Grant, Lucy, and their daughter Jennifer. He's on a mission to find the other three alien gemstones, siblings of the one that gave Grant his superheroic powers - and only Grant can lead the way! Following the gems' trail through time, the four ended up in a future New York City ruled by the fearsome entity known as THE SMOKE - and reclaimed one gem. They set off in the TARDIS and arrived at their next destination... a world where the Harmony Shoal has taken over. But Grant's powers have ceased working - just as