Are you in the mood for a mystery? Right now, a judge and a couple teams of lawyers are working on a great one — the case of the disappearing, reappearing YouTube video.

Earlier this month, Universal Music Group pulled a wildly popular video by file-hosting service Megaupload off YouTube. While YouTube has reinstated the clip, UMG has not yet said why it requested the video be pulled in the first place. The video only contained original content, though it did feature some Universal artists including and Macy Gray.

Now, Megaupload is putting pressure on a northern California court — and on UMG — to get to the bottom of this troubling takedown.

Megaupload’s video was uploaded to YouTube by the company on December 9. As it started to skyrocket through viral activity, Universal Music Group had the video unceremoniously yanked off YouTube — regardless of the fact that UMG had no copyright claim on any of the content in the video.

All the music was original, and the video’s all-star cast of celebrity endorsers, from Drake and Kanye West to Kim Kardashian and Serena Williams, had signed agreements with Megaupload.

Then, Universal stated the video wasn’t pulled because of copyright issues. In a letter from UMG’s attorneys to YouTube, the studio states, “UMG’s rights in this regard are not limited to copyright infringement.”

In other words, the studio was trying to exert control over content it didn’t own — and therein lies the crux of the mystery: What terms of Universal’s contract with YouTube allow the record label to arbitrarily decide what videos can and cannot be posted to YouTube without any clear copyright claim?

As pressure began to mount and questions began to dogpile on UMG, YouTube reinstated the video. In a statement to VentureBeat, a YouTube spokesperson said, “Our partners do not have the right to take down videos from YouTube unless they own the rights to them or they are live performances controlled through exclusive agreements with their artists, which is why we have reinstated the video.”

However, Megaupload had already filed suit against UMG.

In its response to this suit, UMG has submitted an 18-page response to the court to defend its actions. However, in none of these 18 pages does UMG state exactly why the video was taken down in the first place.

“UMG did not even attempt to defend the legitimacy of its false claims to ownership of the Megaupload Video,” stated Megaupload in its response.

On its website, the company continued, “A powerful and popular viral campaign was stopped in its tracks by illegitimate censorship. It is unfair that we are facing baseless legal threats combined with propaganda depicting Megaupload as rogue and illegal.”

To solve the mystery once and for all, Megaupload is asking the court for permission to do “essential written discovery” on Universal’s private conversations and contracts with YouTube regarding the video takedown.

We’ll definitely be following this case closely and will report back when more information about this puzzling takedown is available.