Lady Caroline appeared in Point Blanc where she pretended to be Alex's mother. She is described as slim and dark haired, very much like her daughter.
In Point Blanc Alex stayed with Caroline Friend and her family pretending to be her son. Lady Careline tried to avoid Alex, she drove into town a few times and spent a lot of time in bed.
Differences in the TV series
In the TV series, Lady Caroline is nearly constantly on sedatives of some form, only half present for any given conversation. Her main interaction with Alex was to ask him why he has been forced to work for MI6, showing compassion for his situation, but says little else beyond that.