Wants to Write a Story About Troll Dolls

Dear Rich: My daughter is a collector of Troll dolls, and I am a published fiction-story writer. Do I need permission to write a fiction story about Troll dolls? You're free to write about the Troll dolls but there may be limits on how far you can go when exploiting your story. 
Backstory. The Troll doll characters are protected under a copyright owned by the Danish company Troll Company ApS. [Disclaimer: We used to perform legal services for the Troll Company ApS and we're still deeply fond of the Thomas Dam creations.] The copyright history has been complex and for a period, U.S. courts considered Troll dolls to be public domain. That ended after the U.S. entered into an international copyright treaty in 1996 and the Troll Company reclaimed its rights in the U.S. (It had never lost them in the rest of the world.). The Troll Company has been active in its attempts to exploit its copyright and its most recent foray looks to be a major movie event  with a release date set for 2015.
Protectible characters. BTW, we have previously written about the protectability of literary, film, and licensed characters. We think that literary publication of your story may be possible under fair use/free speech rights but beware that some uses of characters in literary ventures have been successfully blocked. Beyond literary publication, Troll Company would have a right to halt commercial exploitation -- for example licensing the story for TV or film.