M.J., Heath, and Gilley, are back home in Boston, where their new film is sure to be a monster hit To promote the film, the studio is sponsoring a special exhibit of supernatural artifacts at a local museum. Unfortunately, Gilley--whose mind is engaged with wedding plans--gets talked into donating to the exhibit the very dagger that keeps the dangerous ghost Oru and his pet demon locked down in the lower realms. Before M.J. can recover the bewitched blade, there's a murder and a heist at the museum, and the dagger is stolen.

Now Oru is coming for M.J. and her crew, and he's bringing with him some fiendish friends from M.J.'s haunted past. She, Gilley, and Heath are certain to be in for a devil of a time. M.J. may even need to recruit a certain skeptical Boston detective to help stop the paranormal party crashers from turning Gilley's wedding bells to funeral knells. . . .