"Hank the Cowdog: The Case of the Halloween Ghost" by John Erickson (Book 9)

There's something spooky going on at the ranch! When Halloween arrives, Hank - the self-appointed Head of Ranch Security - has got his hands full of adventure. First, there's a problem with the Tricker Trees. Then the ranch is invaded by two skeletons, a witch, and a pirate. And when Hank goes to investigate a strange sound in the cake house, he's sure it can only be one thing...a ghost. Can Hank rid the ranch of this unwanted visitor? Or is he destined to be spooked for good?