Yekaterina knew that the Marquess of Seberlin was injured.
Did the Marquess of Seberlin know of Yekaterina's subsequent actions?
Of course, he did.
Even, it could be considered that the Marquess of Seberlin tacitly consented to it.
This was the 'compensatory greed' exclusive to nobles.
The Marquess of Seberlin's thought was straightforward: If he was injured, he certainly couldn't just suffer the injury for nothing. There had to be something to compensate for his injuries, and he even aimed to maximize his benefits!
Therefore, under the premise of being 'tonight's patch for Port Doldot,' that Marquess of Seberlin did everything possible within the greatest extent to pave the way for his daughter.
To pave the way for Yekaterina to inherit Seberlin.
However, even with full preparation, the Marquess of Seberlin, to be on the safe side, would not leave things unattended.
There must be someone monitoring this place.
This was Arthur's guess.