Zack stopped outside of the mansion, not believing his situation. There he was, about to step into an abandon mansion in the woods. He couldn't tell if this was really Vinashy's place or if he was just squatting.
At this point, Zack wasn't really scared of either of the people he just met. He still didn't know supernatural beings existed on the level of Virgil and Vinashy, though he couldn't deny otherworldly being were involved in the ritual that took his friends. In Zack's mind he was much stronger, faster, and more skilled than any mugger/serial killer or whatever and had quick healing and regeneration to boot. He followed Vinashy in.