We know for sure that Hackett called Mari, because he said so in writing.
Likely Pak also had conversations with Mari, as Pak was acquainted with Shannan, Mari's daughter and Pak was acquainted with Alex Cross, Shannan's boyfriend.
Pak claims he meet Dr. PCH allegedly for the first time, when Pak and Alex Cross returned to Oak Beach a day or two after Shannan disappeared to look for her.
If Pak's story is true, and the Cross and Pak did not knock on every door in Oak Beach, then they must have met Dr. PCH randomly. I personally find this incidental contact a little hard to accept.
If the 'web sleuthers' here, could determine if Dr. PCH; Pak and possibly Brewer (who we know was acquainted with Pak) knew each other and what was their prior relationship before Shannan disappeared, it would go a long way to either proving or disproving collusion between Pak and Dr. PCH.
What I am specifically most interested in is if when looking for Shannan, Pak and Cross visited Gus Coletti, at all before they met with Dr. PCH.
If I was Pak, and returning to search for Shannan, the first place I would go would be to see Gus, as I know he was the last person besides myself to see Shannan alive. The only reason I would go see Dr. PCH first is if I knew he was the last person to see Shannan alive!
If they went first to Dr. PCH's home, I then have a sense there was a prior relationship, which leads a real possibility of a criminal conspiracy by Pak and Dr. PCH relating to Shannan.