Operation Cain: Shepherd's Mystery

Three murders are committed in a small Yorkshire village. Seasoned senior officer, Saul Catchpole, and his team, get drafted in to solve them. Operation Cain is launched to find the killer and early on the clues seem to lead to the local agricultural college where, on closer inspection, things are not quite what they seem to be, particularly among the students.
Saul soon realises that the murders are only a part of what's going on, and there is a much bigger picture emerging of drugs, explosives and assassinations of foreign dignitaries. To cap it off, he also comes to realise that some of the people in his own force are not what they seem.