After Mel was imprisoned, she helped rescue Mel with the Seventh Doctor. She then tried to flee the city, sneaking Mel out in her mistress's wagon, but they were stopped by the city guard and taken to prison. Mel was able to convince Popidius to allow them both out of prison, but then left to look for the TARDIS.
Aglae and Popidius attempted to escape the city to avoid the volcanic eruption, and ran into the Doctor and Valeria, whom they informed that Mel had gone looking for the TARDIS. The Doctor went in search of her, and the remaining three attempted to escape through the city gates. (AUDIO: The Fires of Vulcan)