An adaptation is a film based on a preexisting work such as a book, a video game, a TV show, or even a cartoon. Even if common, this exercise is often tricky and not only at the realization level !
Indeed, the adaptation of a preexisting work presupposes the acquisition of the corresponding rights. Yet, this can be a very labyrinthic process. You must first determine if the preexisting work is no longer copyrighted. Failing that, you must seek for the author or authors if several or right holders and obtain their permission to use the work.
Then, you must draft the contract of transfer of rights. The latter is indeed a complex agreement according to the extent of the adaptation, its destination (theaters, movie, TV show and so on), and the public targeted. Moreover, the contract can be draught exclusively or not. Last but not least, you will have to negotiate the maneuver room of the director regarding the original work, especially in civil law countries where moral rights are of high influence and can make the exploitation of a movie stopped if the original author feels betrayed by the adaptation.
Lastly, for some adaptations, a whole licensing program can be foreseen, which allows the realization of prequels, sequels and spin-offs inspired by the original work, its universe and characters. It is often the case nowadays for the comics.
You then have to secure the possible right of exploitation for the merchandising which can prove a fructuous business if the movie meets a great success.
Greenberg, Hornblower, Deschenaux & Partners already had the chance to draft transfer of rights agreements for the movie adaptation of preexisting literature works and stays at your entire disposal for all help that is deemed necessary.