In 1940 Kenya as their country prepares for war, the local aristocratic social set lives a decadent, self-indulgent lifestyle, that leads to murder. The same events were also dramatised in the feature film White Mischief, which was released seven months after the first transmission of The Happy Valley.

A Russian ballet dancer defects from the USSR, emigrates to England, and joins a ballet company run by a powerful, wealthy lady (Joan Collins).