The Brood of Erys, by Andrew Smith

Another audio with Colin Baker’s Sixth Doctor and Lisa Greenwood as feisty young companion Flip. This has two very effective concepts – the eponymous Brood, who call themselves the Drachee, horrible malevolent childlike aliens; and the woman who has amnesia, engineered so that she does not know the role she plays in the history of the planet Erys (which itself turns out to have some unexpected secrets). Smith of course wrote Adric’s debut Full Circle back in the day, and has done a couple more Big Finish stories since; I think this is the best of them.