Who was the kidnapper?

I believe everyone is knda suggesting the kidnapper to be the fl's college friend and at the same time some people saying it is the ml's assistant but at the scene of the crime, he was next to the ml all the time or could he be connected to this? Could this be a business organization plotting against her for the ml to like step down on his job or there is even a third party involve? 

What do you all think?