Let's say you are working late at the office one night and your boss's son (your boss is the company owner), comes out of his dad's office with white powder around his nose. You see him. He sees you. What are you going to do about it?That's a great opportunity: if the boss, the father, is a decent man, he'll promote you for telling him about his son. If he gets angry and fires you, good riddance. Nothing complicated there.
If you tell the father, I think it's a career-ending opportunity...or worse.
Even if the father is a decent man, you now hold something (i.e., power) over him and his family. He will quickly realize that he has to do something about you.
None of his options look good--for him or for you.
So, let's imagine you say nothing. The son still knows you have power over him (the son) and, potentially, his father and the company. And, remember, he's a druggy. Ergo, he's inclined to make bad decisions and to take desperate action.
Frankly, I would say that you are in a very bad spot.
I can think of a solution, but it is still loaded with risk (i.e., create a Mexican standoff).