IDEAS aren't copyrightable, only the way an idea is EXPRESSED is copyrightable, and able to be infringed by another work. So no, your novel, all 200-300 pages of it, can't infringe a 3 1/2 minute long music video that had a "script" that was all of 1/2 page long.
Also, only the original parts of a work are copyrightable. Your general plot line has been used many. many times before, but presumably you're expressing it in a unique way, like maybe having the sorcerers all be midgets with yellow hair who dress in gypsy clothing and speak Spanish. Those unique expressions can be copyrighted and infringed. But on the other hand, sorcerers' crystal balls, magic spells, long robes and beards, etc. are called "scene a' faire" and because they're part of the sorcerer character, those kinds of expected elements aren't copyrightable.
When it's time to publish your novel, you'll want to shop for a literary agent, who will then shop it to publishers. Before you do that, you'll need an entertainment lawyer to "vet" the work, because any publisher will require you to warrant and represent that your work doesn't infringe on anyone's rights, including copyright, trademark, publicity, privacy, contact, etc. You're novel will get a "common law" copyright automatically when it's done, but you'll want to protect it with a proper notice whenever you show it to anyone, and also want to register it with the WGA and for a copyright before you do.
Good luck, novels are hard to write.
PLEASE READ THIS BEFORE YOU COMMENT, EMAIL ME OR PHONE ME. I'm only licensed in CA. This answer doesn't make me your lawyer, and neither do follow-up comments and/or emails and/or phone calls, and you shouldn't expect me to respond to your further questions if you haven't hired me. We need an actual agreement confirmed in writing before any attorney-client relationship is formed. This answer doesn't constitute legal advice, and shouldn't be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue.
As my esteemed colleague has indicated, ideas are not protected by copyright law. Copyright law protects original works fixed in "tangible mediums of expression" (such as a book, movie, photograph, magazine, etc). Even if your novel follows a well-known general story-line from a music video or any other source, you probably will not engage in copyright infringement so long as you prepare an original work based on the general story line.
On the other hand, if you borrow heavily from the characters, plot-line, and language used in the music video such that elements of your novel seem substantially similar to elements int he music video, you still could have a problem. For example, if the music video included words to a song that tell the story, and if your book uses the precise words included in the song, you could be deemed to have infringed the copyright in the music video and song. Likewise, if your book depicts a character in a manner nearly identical to the way the character is depicted in the music video, you could be deemed to infringe copyright in the character. Much depends on exactly how much you use of the original material in the music video--if you simply use the general stody line, you won't have much of a problem--but if you copy significant portions of elements of the music video (such as song lyrics and/or characters), the situation could get messier.
As a practical matter, you need to be cognizant of the fact that some people who produce original films, music, theatre and/or music videos are very aggressive in enforcing their IP rights against others. In addition to copyright, there can be trademark, trade dress, right of publicity and right of privacy issues in a situation like this. That is why most publishers have a team of lawyers on staff who review books (and work with authors to change them) before publication to minimize the risk of an infringement suit. You should expect that your literary agent and/or publisher will want to work with you to address these issues. If you "self-publish" it would be a very good idea to seek your own legal counsel. These issues can be tricky, and it is wise to work with legal counsel rather than to rely on the general advice you can receive on web-sites such as this.
The previous answers are informative and helpful. I write only to draw your attention to a recent case that came to mind while reading your question, Frye v. YMCA Camp Kitaki (8th Cir. 2010.) One law firm posted an excellent summary of the case here: http://bit.ly/jUrUiM. The court's full opinion can be found here: http://caselaw.findlaw.com/us-8th-circuit/1535730.html. (I know some attorneys don't like to subject non-attorneys to full judicial opinions, but I find it to be a useful technique to show people how judges think/apply legal rules.)
In short, the Frye court found that once the unprotectable "scenes a faire" elements were removed from a play with a "medieval theme" and “hero-on-a-quest plot," there was no "substantial similarity" with the plaintiff's play that could give to liability for copyright infringement. HOWEVER, keep in mind that a) the substantial similarity analysis can be very fact-specific; and b) it took a lot of time and money for the defendant to prevail in the Frye case. While you might eventually win yours (perhaps even with an award of attorneys' fees, if you're lucky), do you really want to assume the risk of litigation by using a similar storyline?
This answer does not constitute legal advice, and should not be relied on in place of a consultation with an attorney. No attorney-client, contractual, or fiduciary relationship has been formed as a result of this post or anyone's use of it. The only manner in which an attorney-client relationship can be formed with Charles Colman Law, PLLC, is via a countersigned letter of engagement on CCL letterhead. Charles Colman is only admitted to practice law in New York State, and before New York federal district courts. Although he endeavors to answer all Avvo questions knowledgeably, he cannot and does not provide any guarantees as to the thoroughness or accuracy of his responses.
Short answer: No. All the derivative movies and books you've ever seen and read are on the market because nobody gets to own the idea of teen romance, lost love, princess saved by itinerant hero, poor girl saved by prince, or a bunch of sorcerers mooning around and murdering people (Thanks, Harry Potter!). Since nobody owns the ideas, you are by definition allowed to publish derivative stories.
You may have heard the joke that there are only 5 basic plots in all of literature -- well, it's not really a joke (though there is some dispute on what the actual number of viable plots really is (see link)).