We're told the former 'Girls Next Door' are hosting a séance at Holly's house -- which she happens to think is haunted -- and they'll be getting an assist from "Ghost Adventures" star and Hollywood psychic medium Patti Negri.
Appropriately, the paranormal chat is planned for the night before Halloween ... so spirits should be in abundance.
While our Bridget sources say she really hopes to contact her old squeeze, Hef, in the great beyond -- sources close to Holly tell us she's not trying to connect with anyone in particular. Any ol' ghost'll do.
Remember, Holly and Hugh have a rocky history -- she claimed Hugh verbally and emotionally abused her while she was in the Playboy Mansion.
Hugh, who died in 2017 at age 91, famously dated Holly, Bridget and Kendra Wilkinson back in the day. Since then, Holly and Bridget have gotten super into ghouls and ghosts.
Bridget hosts her own podcast called "GHOST MAGNET With Bridget Marquardt" on Apple Podcasts ... and the séance will be a special edition of her show. The ritual will also be streamed live on Facebook, Instagram and YouTube.
Holly's no stranger to paranormal activity either ... as we first told you, she started dating Zak Bagans after hitting up his Haunted Museum in Vegas.
Hef's Halloween parties at the Mansion were legendary, so this could be his time to shine ... again. Bridget hopes so, anyway.