Summary:simeler to the live action Scooby doo movie the teen detectives and gravity falls Gang are called in to investigate strange going ons on spooky island
(we have Frank Dally Veronica and Andy and their talking sheep dog Snoopy-Doo wrapping up another Mystery)
Veronica:And the Luna ghost is in fact......
(pulls off mask reviling a middle age Caucasian male in his fiftys)
Gang:Old Man Smithers?!
Factory owner:the creepy janitor?
Veronica:Smithers wanted revenge after you refused to pay him triple.
Smithers:yes and I'd have gotten away with it too if it hadn't been for you meddling kids and you dog.