Looking for the title of a book and/or author I read around late 90's early
2000's. A family is held hostage in an English country estate by 3 or 4
Men. Unbeknownst to the family the son is in on the plot. The father
Works for either a biological or chemical testing or manufacturing
Company. 2 adolescents are hidden away in an attic space that only they
Know about and watch the scene unfold. The hostage plot awry and people
Are killed including a philandering French son-in-law who tries to seduce
One of the guests.