The Doctor and Flip arrive in a cave/mine, and run into an expedition, so what's in the mine?

Its good to have Flip, I've not heard a lot of her stories, but she nice enough.

The story is, or at least starts out fairly easy going, The Doctor and Flip join forces wth the expidition to explore the mine. The Vortex Ice seems to be frozen time and there are one or two twists along the way. Part two begins and initially you feel as if you've missed a bit. Its hard to not to spoil it so stop reading now, but we find two of each Flip and The Doctor the present ones and a future ones. This is where it gets very easy to lose your place, as you're not sure which version your currently listening to, as not only do they share scenes they're also trying to hide the fact.

I enjoyed it, but I feel thats it one I need to give another go to to really understand it.