great story idea

It is a historical psychological drama thriller type thing, about a fictional figure head and a mysterious death and the person least expected is guilty though the killer had not premeditated their role is assisting a death.

I had the idea as I researched about fat trapping away toxins like pesticides, I thought maybe a monarch would be genetically predisposed to with stand attempts to poison them, and it would be long forgotten anyhow, until they begin to become overweight and look to loose weight, thereby releasing toxins that  overcome the body and cause death, all because someone suggested a way to loose weight successfully....murderer?

It would make a good story!