Arthur went back to the fighting ring that night to liberate the men and women that were force to fight in death matchs. He earned a lot of karma by doing so.
He also raided the fighting ring which earned him a lot of money. The money he earned from the place and Irvin made a total of 213 gold coins that he earned that night.
The following day, he began investigating the R brothers and Irvin's other accomplices. From the R brothers, he learned about Jake's involvement in his attempted murder and Jake's support of the crime ring in the city.
Getting to Jake was easier than he expected. All he had to do was lure Jake over with an invitation to a brothel from the R Brothers.
The man only had the cultivation of the ninth transformation of the first mortal coil despite his advanced age and wealthy family. So it was easy to subdue and kill Jake.