It's fine, I guess.  I enjoyed having a story focused on Nyssa and the Doctor along with the dark and lonely ambience the story easily established.  Part of that is owed to Sarah Sutton's great narration.  I think the problem is a little deeper though.  The story itself felt a little bland and predictable.  It really didn't stick with me in any meaningful way.  So it feels like a competently made and written Short Trip, one that was a very easy listen, but one that also didn't quite leave much of an impression on me one way or another.