Mostly Ghostly - Have You Met My Ghoulfriend?

the long version

Nicky and Tara still live in Max's bedroom, and while they've found some clues, they still don't know what happened to their parents. Meanwhile, Phears is still desperate to get his hands on Nicky and Tara, and to pressure Max into turning them over, Phears brings a Berserker Ghoul to inhabit Max's body--and make Max go berserk when he least expects it! But Max, Nicky, and Tara aren't giving in to Phears. They have a few tricks up their sleeve--like one very talkative ghost cat, who's taken residence inside the tunnel to the ghost world. . . .From the Hardcover edition.