From season 2 of the Inspector Lynley Mysteries is "In the Presence of the Enemy," which concerns kidnapping, murder, politics, and mental instability.
The editor of a newspaper, Dennis Luxford (James Hazeldine), finds out that his child by a left-wing black politician, Eve Bowen (Sophie Okonedo), has been kidnapped. Luxford himself is a conservative; Bowen is a government minister and the two have never revealed their connection or that they have a child. Luxford is warned that he must publish the details of his first-born, or she will be killed.
Unfortunately, the girl is found dead, and later, his son Leo is kidnapped. Lynley (Nathaniel Parker) and Sergeant Havers (Sharon Small) have to go back into the past and to another town to solve the mystery and hopefully get Leo back in time.
Lynley's love interest, Helen Clyde (Lesley Vickerage), is a friend of Luxford's and tries to help him, which in turn complicates her relationship with Lynley.
Excellent entry into the series, with everyone in top form. I can never figure out what Parker sees in Clyde, but that's another story. The script and production values in this episode are excellent. Highly recommended.