This is one of the earliest of Brian Clemens's "Thriller" series. It is not one of the better efforts, although it is a clever story, has one outstanding character, and a slick climax.
In this story an American couple visit London. While there the husband begins to behave extremely strangely, referring to someone called "Theresa", whom no-one knows, and even attacking his wife. Periods of normal, lucid behaviour are punctuated by outbursts. His wife calls for help that leads to the unorthodox detective Matthew Earp. Earp uncovers a tale of espionage that puts the couple at risk ..
The action moves very slowly, which is hard work for the viewer, and the story is very complex. The outbursts by the husband become very irritating. Things pick up strongly with the arrival of Earp, played with camp abandon and panache by Dinsdale Landen. However his comic style isn't wholly right for a tale of fear and suspense like this.
This is still worth seeing, and you have more chance of doing so as it was one of the few episodes released on video.
