The Rescue:

Arriving on the planet Dido in the late 25th Century, the time travellers come upon a crashed spaceship from Earth. Its two occupants - a paralysed man named Bennett and a young girl, Vicki - are living in fear of a creature called Koquillion, a native whose people have apparently killed the other members of the human expedition.

However, the Doctor quickly deduces that Koquillion is in fact Bennett in disguise; it was he who killed the others in order to conceal an earlier murder he had committed on the ship..

The Romans:

The four time travellers are enjoying a rare holiday, staying at a villa not far from Rome in the year 64 AD. The Doctor soon becomes restless and sets off to visit the city, taking Vicki with him. In their absence, Ian and Barbara are kidnapped by slave traders.

Having been mistaken for the famous lyre player Maximus Pettulian and asked to perform at the Emperor Nero's Court, the Doctor has to devise ever more elaborate schemes to avoid revealing that he cannot actually play the instrument.

Ian meanwhile becomes a galley slave, while Barbara is sold to Nero's slave buyer Tavius at an auction in Rome. Ian and a fellow slave named Delos escape from the galley when it is wrecked in a storm and make their way to Rome to try to find and rescue Barbara.