Adrian became a partner in Dunn's PI business and then found out that he specialized in dealing with the paranormal. Past his initial skepticism, Adrian is now very much a part of Dunn's work, just as Dunn is part of Adrian's life with his little daughter, Nessie.
When Dunn is called back to a place which holds terrible memories and more than one ghost, he wants to leave Adrian out of it, but that's not happening. Adrian insists on being by his side, but Dunn might be proved right when Nessie is nearly used as a pawn.