The Revenants by Ian Potter and directed by Lisa Bowerman.
This was a free extra that came with the special edition version of The Light at the End. It's a First Doctor story narrated by William Russell as Ian Chesterton. I don't normally like the companion chronicle stories where there are only one to two characters telling the tale instead of a full cast audio drama but this was splendid.
It helps that it has a framing device of a much older Ian telling the story to a woman he meets on a ferry. This also means that William Russell doesn't have to try and sound like his younger self. The writers have cleverly included several chemical references which makes the most of Ian's background as a science teacher. And it has an eerie ghost story feel to it. All this plus William Russell's only performance as the First Doctor which is lovely stuff.
An unexpected delight and a great bonus, 4.5 out of 5 stars.