State of Change — Christopher Bulis

‘In less than 25 years the Romans have invented electricity generation, airships, radio and who knows what else. Is that reasonable?'

Ancient Egypt, 41 BC. The Doctor and Peri watch as Cleopatra's pleasure barge glides up the Nile in preparation for her fateful meeting with Mark Antony. And an alien presence observes the TARDIS, waits for it to dematerialize, then pounces.