Max's sudden arrival was noticed by Max. And that's why he tried to avoid her. He left the house when the vampire king was coming. And none of his family knows where he went.
Everyone was afraid of him except Darius. Because if they go back in time, they had childhood friends before they became vampires. The difference is that Fabio is two years older than Darius.
"If I may ask, what's the matter, Fabio?" asked Darius.
"Ah, Darius... My friend... Your son and I have a business that only we know about. By the way, come over to the castle sometime. Maybe we can have a drink and a meal together."
Actually, everyone already knew what Fabio was coming for and discussing what. But indeed all of Max's family act like they don't know what business Max and Fabio are in.
"Thanks for your invitation, Fabio. I'll think about it," said Darius.