The Fourth Doctor Boxset

The Fourth Doctor Boxset is a collection of two audio dramas by Big Finish Productions based on the long-running British science fiction television series "Doctor Who". The stories were written by Robert Banks Stewart and former "Doctor Who" producer Philip Hinchcliffe, who had previously worked together on two stories of the thirteenth season of the series, "Terror of the Zygons" and "The Seeds of Doom".
The Foe from the Future.
by Robert Banks Stewart (adapted by John Dorney)
Plot.
The TARDIS arrives in Devon, in the year 1977. But history is unravelling. At the centre of it is a seemingly haunted manor owned by a mysterious man named Jalnik.
The Valley of Death.
by Philip Hinchcliffe (adapted by Jonathan Morris)
Plot.
In 1870, Professor Cornelius Perkins mounted an expedition to the Amazon rainforest and was never heard from again. A century later, his great-grandson flies to South America looking for answers. Joining him is the Doctor, on a mission from UNIT, investigating rumours of a crashed UFO.