Set during the reign of the Roman Emperor Nero at the time of the Great Fire of Rome, the serial has the First Doctor (William Hartnell) and his new travelling companion Vicki (Maureen O'Brien) investigating intrigue surrounding the death of a lyre player who was on the way to perform at the palace of Nero (Derek Francis) in Rome. At the same time, Ian Chesterton (William Russell) travels to Nero's palace to save his fellow schoolteacher Barbara Wright (Jacqueline Hill), who had been sold to Nero's wife Poppaea (Kay Patrick) as a slave.