One of the best 3rd Doctor stories I have heard so far.

The first half of this story is incredibly atmospheric and creepy, and the conversations with the tape recordings make a good use of the audio medium. The entity inside the tapes is a very creepy concept, in a way it reminds me of The Idiot's Lantern, but more well done.

It does slow down a little when The Doctor arrives in part 2 but overall this story is amazing