Grey and his friends paid their respects to the Second Prince before heading inside to meet with the Seventh Prince. Due to the Second Prince's intelligence, Grey wanted to reduce their contact to the bare minimum. He would speak with him only when it's absolutely necessary.
The Second Prince wanted to stop them, but seeing that they had no plans of staying, and he was also having a conversation with one of his people, he let them leave.
They soon went to the Seventh Prince's chambers.
"When should we make a move?" Klaus asked, of the trio, he was the one who had more people under his palms. With the help of his ice ability, he released bits of ice particles into their bodies, little enough that they wouldn't notice, but enough that when merged together, these people would die on the spot.
It would be practically impossible to figure out who did it.