I listen to a lot of these shows online. The Heel of Achilles is one of the few episodes I have on cassette from when I was a kid. 
This episode is one of my favorites; as the quality of episodes can be hit or miss (I skip almost all episodes authored by Elspeth Eric), I really appreciate one like this that has reasonable pacing, a storyline that works, no repetition in dialogue, and a believable twist.
A haunted house? A rich guy insecure about his relationship with a much-younger wife? An insightful psychiatrist? Classic elements of a good mystery. Enjoy this one! 