It was either return or proceed and Lia chose to proceed. This option had many different ways to go about. If Lia paired up with Third P she couldn't use her power. So, it was best to let Noel go with him.
Third P might be out of his mind at the moment but she believed Noel could take care of things on his end.
The other reason was that Lia felt First P knew something and she needed to find out what it was. Lia called out to her corpses and waited for them. She didn't want to use the corpses in the laboratory.
If Second P and First P were dead, it'd benefit Elder P but he also had to be wary of the murderers. He would suspect his other two siblings but he couldn't act quickly as he still needed to consider the purpose of this facility.
The goal for Lia and Noel was to completely get rid of the P family and destroy the facility. They calculated the plan would take at least a month to set into motion but never anticipated that matters escalated to this point so quickly.
