This is a horrible episode to watch. What you have is a family, the Penmores, who have lost their family fortune through bad investments. Rather than accept what they have done to themselves, they harass a local family who are totally innocent but because of the worst policing I have ever seen an innocent baby is killed and a decent family is destroyed. There is no doubt all of the responsibility falls on DI Lane who fails completely in arresting one of the Penmores after he makes direct threats of violence against Laura Kessell and her baby.
It seems DI Lane is weak and afraid of the Penmores. Det. Supt. Wycliffe has been absent because he has had to attend a funeral for one of his wife's minor relatives when he should have been on duty; but for his wife he had to be where she wanted him to be. Upon his return to the station, Wycliffe asks the questions his staff should have asked and finds a potential subject; and that subject is the one who is able to identify the guilty party. But while Wycliffe is arresting the actual murderer, DI Lane failed to provide even one officer as protection for the family that has been threatened.
The Penmores and their friends attack the Kessell family in their home; and before the police arrive it is too late to save the family. It's a tough episode that makes you wonder about policing in Cornwall in the 90's.