What's the Name of That Book??? discussion

I'm trying to find a book/series I read in junior high. It was like a combination of Narnia and Lord of the Rings. It was a Christian fantasy series where the protagonist (a boy) in the modern world and journeys through some kind of portal to a medieval-esque Otherworld. I remember his father is missing and went through the portal, and that the rightful king of the realm is imprisoned, and there is a dog who turns out to be an girl who was enchanted by the antagonist, an evil sorcerer. Please help!

Some long shots:
The Dry by R.L. Nolen?
The Fall by Garth Nix?
The Book of Time by Guillaume Prévost?

Beccah, around what year did you read this book?

Can you describe the portal and its location? Do you simply walk through the portal to enter the other world?

Kris,
It was around 2001-2003 and I'm pretty sure the portal was just an ordinary looking door that you walk through- I kinda remember one scene where it door opens onto the dungeon where the king is being held and the villains wonder how the protagonist got into the cell (the portal vanished).

Sounds like The Sword Bearer, by John White.

THAT'S IT!!!!! OMG, thank you Abigail!!!!!!! :D

Yay! You're welcome!