Arthur read the letter addressed to him carefully. Since this letter came from one of the royal families, he had to know the contents of the letter and the implied message conveyed to him.
A small truth was seen in the contents of the letter.
Niko or his childhood friend had a big connection to the underground rebellion movement that wanted to overthrow the royal family. Various evidence that had been collected pointed to Niko which somehow looked like evidence that was made up by someone.
Realizing the oddity of the report given by Niko based on the evidence found, it made him worried that the thousand gold coins owed to Niko had moved into the hands of the royal rebels through hands that were not visible to the investigation.
"Well, you are really in big trouble Niko..." Arthur muttered as he read the contents of the letter more carefully.