SOLVED. Fantasy book - Child's parents vanish, uses rings on doorway to open portal to fantasy world. [s]

[Dylan]

My dad used to read me this book when I was a child 13-ish years ago. A child uses ring(s) a family member used to own to open a portal to a fantasy world.

My memory: i remember the door being located in a sort of basement-armory the parents used to use before they vanished.

My dads memory: the book was about the childs parents disappearing, and the kid chasing their whereabouts after discovering the ring(s) left behind (or found?) Could be used to open a door to a fantasy world.

We're both tired of googling, any help would be appreciated.

[Becca]

Son of the Hero by Rick Shelley has rings that have to be worn and held against a door. The protagonist is 21, though, so it might be for slightly older readers than the book you're looking for.

[Dylan]

That's the one! Thank you very much!