Lets really think about what Oliva did at that boat party...
Here's the whole conversation:
We played chess dozens of times and he always beat me.
So I got interested in him.
One day the idea came up... of meeting to play face to face.
He invited me to a party where there would be important people.
In his house?
No.
Not in his house-- on a boat.
On a boat? Why?
That's what I wondered too.
Why on a boat?
Then I found out.
It had to be out at sea because at that party... things happened that would be illegal in any country.
You want to know what things?
Come on.
Dare to ask.
No, forget it.
At that party... things happened, and the things that happened made me go back more times.
Wait a minute.
Couldn't that guy
have organized all this?
No.
Why not? He's idle, eccentric, smart, rich. Why can't he be...
It can't be him because he's in here!
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Okay, so we know:
1. It's illegal in most countries.
2. It had to be done out at sea, on a boat.
3. It's addictive.
4. There are important people in there doing it.
5. It has to be something shocking that a smart person wouldn't figure out even after knowing 1, 2 and 4.
What possibilities could there be that meets all 5 criterias?