The Doctor and Gabby arrived in ancient prehistory, only to be attacked by giant, sentient, flying metal discs. The Neanderthal Medicine Man, Munmeth and the time-travelling duo set out in search of these discs, which had been kidnapping groups of humans – Neanderthal and Sapiens alike! Their nefarious purpose: pitting human species against one another in a gladiatorial arena of death! With the help of a gang of intergalactic bounty hunters who have followed the Monaxi discs through space and time, the Doctor, Gabby and Munmeth attempt to put a stop to this cruel sport… but it seems as though they’ve only succeeded in angering the enemy into creating a temporal tornado. What could be waiting for them on the other side?