There are still eight months between us and the December 23 release of The Adventures of Tintin: The Secret of the Unicorn.  But producers Steven Spielberg and Peter Jackson have, from the beginning, scoped their Tintin adaptation as a trilogy.  The Secret of the Unicorn is the eleventh title in the Belgian comic series, so Spielberg and Jackson are not tied to the release order of the source material.  This raises the question: what might serve as the basis of the sequel to Unicorn?

Our partners at Omelete may have found the answer in a post at On the Go informing of a promotional appearance by London author Anthony Horowitz.  The attached bio indicates Horowitz "will be writing the screenplay to the second Tintin film, Prisoners of the Sun."  Details after the jump. [Update: Horowitz has confirmed that he's writing the second film.  Hit the jump for quotes on the gig from the author]

The synopsis for Prionsers of the Sun, the fourteenth title in The Adventures of Tintin:

the-adventures-of-tintin-prisoners-of-the-sun-book-cover

After The Seven Crystal Balls set the eerie stage, Tintin and his friends continue their adventures in Peru. There Tintin rescues an orange-seller named Zorrino from being bullied, and the young man becomes their guide in their quest to find the Temple of the Sun. But they find more than they bargained for and end up in a hot spot. The perils of this engaging two-part adventure are especially harrowing in their combination of the supernatural and the real, although the resolution is a little too deus ex machina. Calculus and the Thompsons provide their usual comic relief. [Amazon]

I wish I didn't have to apologize for being American and ignorant every time I write about Tintin, but I have no idea what any of that means.  Yet there it is.

We'll treat this as a rumor for now, but it's a reasonable hypothesis.  Horowitz's publicist may have released the information about to promote his author earlier than Paramount was ready to announce.  And as a writer, Horowitz is the kind of talent that Jackson and Spielberg would pursue.  Horowitz has a number of credits on British television, most notably as creator of the WWII drama Foyle's War.  Perhaps tellingly, all three writers credited on the Secrect of the Unicorn screenplay -- Stephen Moffat, Edgar Wright, Joe Cornish -- have also written for British television.

At Comic-Con in 2009, Jackson mentioned his preference for Prisoners of the Sun as well as The Seven Crystal Balls, the book that precedes it.  Jackson also said writing would begin before the release of The Secret of the Unicorn.  So really, the title and the timeline fit.

Steven Spielberg is using motion capture technology to direct Jamie Bell, Daniel Craig, Andy Serkis, Simon Pegg, and Nick Frost in The Secret of the Unicorn.  Jackson is on board to direct the sequel.

For those who want to sample Prisoners of the Sun, this appears to be a full 38-minute animated adaptation:

"Nuts to the sharks!"

Update: Horowitz confirms his involvement to Bleeding Cool and explains:

If that [Secret of the Unicorn] is a success and works and gets an audience I’m writing the sequel to it, Prisoners of the Sun, which Peter Jackson is going to direct.

Horowitz also says he's currently the only writer on Prisoners of the Sun, but he expects to be joined by other writers:

At the moment on the second one it’s just one but you can bet your bottom dollar that by the time the film hits the screen, if it ever happens next year, that I’ll be joined by one or two other names there.