Steven Spielberg and Peter Jackson's The Adentures of Tintin hasn't even opened in the U.S. (at the time of writing this), but is already a critical and financial success, having scored a 82% rating on Rotten Tomatoes and raked in $233 million at the worldwide box office (with a good deal more expected from its U.S. run).

Given TinTin's success, it's safe to assume that Jackson and Spielberg will be moving ahead with their original plan of trading duties on the sequel film, with Spielberg handing the directorial reins over to Jackson, while Jackson hands the producing job over to Spielberg. However, the question still remains: which of the Tintin adventures penned by creator Georges Prosper Remi (a.k.a. Hergé) will Jackson use for the basis of his sequel film?

For those not familiar: Tintin was originally a comic book character featured in a variety of serial adventures; the Tintin movie incorporates elements of the stories "Secret of the Unicorn", its sequel "Red Rackham's Treasure", and "The Crab with the Golden Claws". The latter story chronicled the meeting of Tintin and his longtime friend, Captain Haddock, while the former books were a two-part of adventure about Tintin and Haddock discovering a long-lost treasure (their quest in the movie).

However, Tintin fans will also remember that "Red Rackham's Treasure" introduced another character who would go on to become a fan-favorite: eccentric bumbling genius Professor Cuthbert Calculus, who was noticeably absent from the streamlined story of the movie.

Well, in talking with The Playlist, producer Kathleen Kennedy delivered the latest word on where the filmmakers are in terms of deciding on the story for the Tintin sequel, and it seems that Professor Calculus may be a focal point of the story - instead of the long-rumored "Prisoners of the Sun" comic, which saw Tintin and friends discovering an ancient Incan civilization.

Said Kennedy:

Prisoners of the Sun' was a very, very early discussion, and it isn't under discussion anymore. We've still got Anthony Horowitz working on the second movie, and we don't know what we're doing with the third movie yet. We knew [with the first movie] that we needed to introduce Tintin, we needed to introduce the relationship with Haddock, we knew [the dog] Snowy was going to be in it, so now what we're thinking [for the second film] is what new characters do we want to introduce? Well, we'll probably introduce Calculus and bring him into the fold.

The guys at The Playlist knew their stuff well enough to realize that aside from "Red Rackham's Treasure", there was another story - "The Calculus Affair" - that heavily focused on the Professor, and could be a fitting introduction for the character to join the movie continuity. When pressed on whether or not that was the idea they were working with, Kennedy said "We haven't decided yet...but that's the direction we're headed."

Like the last Indiana Jones movie (Kingdom of the Crystal Skull) attempted to do, "The Calculus Affair" trades the treasure-hunting adventures of the 1940s serials for the more sci-fi-minded era of the 1950s. The story has a decidedly more spy-movie feel to it, as Professor Calculus is abducted after it's discovered that he is working on a sonic device that could be utilized as a terrible weapon. What ensues is a game of espionage, as Tintin and Haddock race across Europe tracking clues to help them recover their lost friend. (Sidenote: You can actually watch the cartoon version of the story HERE.)

While Kennedy is non-committal in her words about the Tintin sequel, using "The Calculus Affair" as its basis seems like a prudent (and likely) move. With a bit of retooling, the story could effectively introduce a new character to the fold, and deliver a second Tintin movie that is different in style and tone - rather than being a slightly different version of the first film. Of course, some may argue that other, more fantastical Tintin stories would be a better fit for a director like Jackson, whose two-part adaptation of The Hobbit is currently in production.

For more on what the filmmakers have planned for a THIRD Tintin film, head over to The Playlist.

The Adventures of Tintin will be in U.S. theaters on December 21, 2011. It's already playing in the UK markets.

Source: The Playlist