It seems the major selling point of this adventure is its bizarrely structured narrative, chopping and changing from the present, past pre-Nissa's torture and post Nissa's torture. This works for a bit, keeping the listener guessing as to what actually occurred and why...but the story shoots itself in the foot with the end of Part 3, which, ok, leaves a few plot points untied but still features the traditional 'parting of the TARDIS' closing. I actually thought the whole thing had finished at this point and i would have been happy (well, satisfied) if it had been the end. To this end, part 4 became a mere explanation of things you didn't know and was almost surplus to requirement. The story itself, once you break it out of the narrative mess, is quite original and topical (all to do with environmental pollution) and both Peter Davison and Sarah Sutton deliver reliable performances: but on first listen, you'll be confused. On second listen, you'll understand. And on third...well i haven't been tempted back for a third yet. And this says much for the rating, as some of my favourites i've listened to several times. I'm not telling you not to give it a go, but there are several excellent adventures out there. This isn't one of them.