Roots: Close Encounters of the Third Kind (Charley's musical duet with the sound creature). Charley attempts to sing 'Freré Jacques', 'Will no man rid me of these turbulent tunes?' is an alteration of the words attributed to King Henry II regarding the desired murder of renegade priest Thomas a Becket in 1170. [Will no man rid me of this turbulent priest?]
Goofs: Though they have spent 50 hours or so in the void by the first time Charley regains sensations, she doesn't immediately croak from dehydration, or have an urgent need to go to the lavatory.
The Doctor and Charley clap after one of the creature's performances, but then shortly after find they've been holding hands so long their hands are fused together.
Technobabble: 'What do you know of transmarginal inhibition?'
Dialogue Disasters: Three cheers for the most overused line in DW history: 'We must get back to the TARDIS!'
Dialogue Triumphs: 'We're not dead' 'Terrific' 'At least not yet. We should keep our options open.'
'I must say I do find our continued existence very frustrating.'
'Even an inhuman voice from outer space got the point, but not you.'
Charley sings 'Dun na na na na na - don't know what the words are - bing bang bong.'
Double Entendres: 'Get down behind the console with me...'
'I doubt anyone at the philharmonic would release our footsteps on CD.'
Continuity: The new universe (which the Doctor and Charley have arrived in) has no concept of time - though fortunately for us time does pass or there would be no story. It also takes a while for their other senses to adjust, though this might simply be a function of the experiment.
Time Lords have senses other than the usual five - all their extra senses are related to time. In a universe with no concept of time, the TARDIS can have no existence. Time Lords are capable of living thousands of years. The Doctor has lived a thousand years of life.
The Doctor theorises that they've become part of a scientific experiment, but this is never confirmed. The environment seems to speed up evolution, including a sound creature evolved from the sounds the Doctor and Charley introduce, and an unspecified organism, which the pair are able to eat.
The Doctor says at one point they'd been walking for the better part of a week (though Charley perceives it as a lot less) and other references indicate this adventure takes many weeks to unfold.
The Doctor wishes to die alone. The Time Lords have a theory that the Doctor's companions are to remind him of death, but he doesn't agree.
Charley wears a broach passed down the maternal side of her family and passed on when the daughter reaches 16.
Location: A new universe, contained in a circular tube, possibly as part of some unspecified experiment, presided over by the Kro'Ka.
Links: 'The Creed of the Kromon', 'The Natural History of Fear' and 'The Twilight Kingdom' are all referred to by the Doctor.
The Bottom Line: 'I love you.'
Big Finish's attempt at doing a 'The Mind Robber' episode one; a simple but effective plot, serving mostly as an examination of the Doctor and Charley and their relationship. Talky (even for an audio story) and over-explained, with a 'deduce the alien's nature' storyline heavily reminiscent of 80s Star Trek. The constant examination of the never-very-interesting Doctor-Charley love subplot gets exceedingly wearying long before the story comes to a close.