For some reason, this episode has a special place in my Doctor Who memories. Maybe it's the geological-based alien, the crystaline costume, the moving severed hand like an old 50's horror movie. So much to choose from. Be sure to take time to view the extras and listen to the commentary track on this one. A lot of fun.
For historical Doctor Who significance, this was the last classic series appearace for Sarah Jane that was not a special.
This set of three classic Doctor Who stories encompasses the Master getting (stealing) his new body, the 4th Doctor's death/regeneration, and the 5th Doctor's post-regeneration struggles. The departure of Tom Baker as the 4th Doctor (who was in the role the longest uninterrupted) marks a distinct change in the style of the classic Doctor Who stories. Not all fans agree that was good. It's up to you to decide, but this set is a great primer covering that transition. On the technical side, this is a beautiful 3-DVD set. The classic Doctor Who DVD's just get better and better as the restoration team continues to do an amazing job making the picture and sound better than it ever seemed at the time of broadcast. Also, more and more extras are added, including production background information and other retrospectives, featuring many of the cast and production team.
What's great about it: Complete story line with all three stories included in the set; excellent DVD transfer; great extras