Mrs. Marigold's House

"Melissa Yuan-Innes delivers a Bradburyian shocker in 'Mrs. Marigold's House'.....Highly recommended."-- Paul Di Filippo, Asimov's

Every Hallowe'en, Mrs. Marigold invites only six children to her mansion.  One boy, Adam, warns Ashley away, but her parents, desperate to get in good with the richest woman in town, force her to go. 
Trick or treat?
Trick.  Definitely trick.
The question is if Ashley can escape the mansion alive.