This fact sheet covers the basics of copyright as applied to producing an “updated” or adapted version of another’s work.
Many great films are adaptations of other writer’s works, from best-selling novels (The Firm, The English Patient), to plays (Barefoot in the Park, Hamlet), to biographies (Patton), and even non-fiction (All the President’s Men, Civil Action). There are also continuations of series, new works with the same characters, etc.

Before you take the steps to do an adaptation of someone else’s work, it is best to get the copyright holder’s (usually, but not always, the author).
If a work is still in copyright, 'updating it' will constitute an adaptation of the work, which is an act restricted by copyright, assuming the work to be a literary, dramatic or musical work. You need permission from the copyright owner to make any such adaptation, usually in the form of a written release as an option agreement. This also applies if you’re writing an original screenplay based on several authors’ works, as usually occurs when an historical piece is written. Sometimes you can find a way to reach an author, but usually it means a lot of enquiry work.

There are certain acts which are permitted by statute even in the case of copyright works.
Examples of these are where the material is created for research and private study, or for criticism and review, or for news reporting or for educational use or for libraries and archives or parliamentary and judicial proceedings etc. If, however, you want to exploit the updated work for commercial purposes, these exceptions will not help you.

The copyright owner from whom you need permission will not necessarily be the original author, who may have assigned his copyright to a third party. Or even if he has retained the underlying copyright, may have granted exclusive rights by licence to a third party, either generally or to some restricted extent.

Depending on whom holds what rights in the original work, you may need permission from several different parties. If the original author is dead, you may need to contact whoever is charged with responsibility for administering his estate, or possibly his literary executors, if he has any, in order to obtain the required permission.

Moral Rights

You should also be aware that, even if not still the copyright owner, the original author has certain moral rights which are separate and distinct from copyright and which cannot be transferred, although they can be waived by the original author only (i.e. not by his assignees or licensees).

One of those moral rights is the right to object to derogatory treatment of the original work, e.g. if it is mutilated or distorted or otherwise dealt with in a manner which is prejudicial to the honour or reputation of the original author.
If your proposed update falls within that description it may be challenged on that ground by an author who is particularly sensitive to his moral rights. He also has a moral right to accreditation as original author of the work and a right not to have someone else's work (such as your adaptation) attributed to him.

The right to accreditation only applies, however, if 'asserted' either generally or specifically, by the author concerned. You must therefore be careful, even if you get permission to make the adaptation, not to credit the adaptation (as distinct from the original work) to the author, and to credit the original work to the author if his right to accreditation has been asserted. Any such assertion is usually contained in documentation relating to dealings by the author with his copyright. Although the above-mentioned moral rights are not transferable, they do pass on the author's death.

Conclusion

You need to track down all parties, which have any continuing copyright interest in the work, and even if these do not include the original author, you will need to contact him or if he is dead then the persons receiving or administering his estate, and seek permission from all of them which, of course, is unlikely to be forthcoming, if at all, without payment of a royalty and/or whatever other sum is considered appropriate for any commercial exploitation of your proposed 'adaptation'.