The Sapling, the Doctor and Alice learned some uncomfortable truths when they came across a huge spaceship… in what was supposed to be completely abandoned space. Once inside they were met with enormous microclimates filled with everything from pterosaurs to burning suns. It turned out the ship was a Memory Ark, containing the entire long-dead civilization of the Xerxes. But this last testament to an extinct race was under threat from the memory-stealing Thrakes – until the Doctor allowed them to gorge themselves on memories to the point that they were destroyed, keeping the Xerxes’ memories preserved forever. Now the three TARDIS travellers continue their journey…