It's the Fifth Doctor with his full Tardis crew of Nyssa, Tegan and Turlough again, and it's the conclusion to a series of linked stories about the search for a cure for a deadly infection called Richter's syndrome. On the planet of Valderon it seems that an effective treatment has been found, but Nyssa meets a man who turns out to be the son she hasn't yet given birth to, in a strange Doctor Who timey-wimey way.
This is a terrific story for the Fifth Doctor and his companions. The twists and turns along the way, and the different timelines really kept me engaged and entertained. But it's the reveal of the villain of the piece that was the real surprise. This is a story that nods to the history of the Doctor and the Time Lords from the classic series, but also references events and stories from the new television series. I can't really say anymore than that without giving away the plot, but if you are looking for a good recent example of Big Finish's work then try this one.
Peter Davison is fantastic as ever, he has always been one of the most likeable of the Doctor's incarnations and that remains the case in this adventure. But this story really belongs to Nyssa and Sarah Sutton gives one of her best recent performances. In particular her scenes with her adult son who, in a neat touch, is called Adric are quite moving. Understandably Tegan and Turlough take more of a back seat role for this one but all of the actors were fine with no jarring notes. And as ever the sound design and music help this along nicely.