The Ghost Bride of Hagglethorn Hall

[Original 13 Ghosts 'verse, post-series] The Scooby gang, plus 3, return to the site of one of their previous cases, reuniting with an old friend, who is also plus 3. Determined to get to the bottom of this new mystery, the two squads investigate, only to find that they might be dealing with more than one haunting... and that one of them might be real.