It's like the plot from a movie: Thieves break into a locked office and copy secret documents closely guarded by a presidential candidate, then threaten to release them to the public a month before the election if they don't get a $1 million ransom. That scenario may sound outlandish, but the Secret Service is taking the purported theft of Mitt Romney's tax returns seriously enough to open an investigation. Romney has released his 2010 tax returns and estimates for 2011, but has famously resisted pressure to release any earlier tax documents. Here, a brief guide to the case of the (possibly) missing tax returns:

How did thieves purportedly steal the tax files?

In an anonymous posting to the hacker-frequented website Pastebin, first flagged by The Nashville City Paper, the self-proclaimed thieves say they broke into the Franklin, Tenn., office of PricewaterhouseCoopers on Aug. 25 after a "gentleman working on the 3rd floor of the building" let them in. The "team" then moved down to the second floor, set up shop in an empty office, and when night fell, broke into the PwC offices and copied "all available 1040 tax forms for Romney." The documents were then encrypted, copied onto flash drives, and mailed to the PwC office and the local Republican and Democratic headquarters.

What are their demands?

A cool $1 million, paid in Bitcoins, "an untraceable online currency popular in the criminal underworld," says Chris Taylor at Mashable. Flash drives with the encrypted files will soon be sent to "all major news media outlets," the thieves say, and if Romney fails to pay the ransom to a listed Bitcoin account by Sept. 28, they'll release the key to unlock the files. If the GOP presidential aspirant pays up, the keys will be "purged," leaving the files "a secret forever." But noting that Romney's tax returns "before 2010 will be of great interest to many," the hackers also offer the unencrypted files to anyone who pays the same $1 millions before Romney does. "Whoever is the winner does not matter to us," the note concludes.

Is this theft plausible?

"The posts and scenario are bizarre enough to warrant deep skepticism," says John Herrman at BuzzFeed, but PwC and the Secret Service are taking them seriously enough to open a formal investigation. Oh, come on, "this has got to be total nonsense," says Julia La Roche at Business Insider. Not only is the story of how the returns were purloined "implausible," but "an anonymous post on Pastebin asking for Bitcoins? That's basically a parody of hackers." Well, at least the part about sending the thumb drives to the GOP and Democratic headquarters is true, says Josh Adams in The Tennessean. But neither office took the threat seriously until the Secret Service called. "A million dollars seemed kind of low," says Williamson Co. GOP chairwoman Jean Barwick. "If you're going to go for a million, why not go for $100 million."

What happens next?

The Romney campaign is referring all questions to PwC, which says it has uncovered no evidence that there was any unauthorized access to any data in the office. But "whether or not the hackers are blowing smoke, attempted blackmail of a presidential candidate is a pretty serious offense," says Mashable's Taylor. And the Secret Service should be able to handle this case fairly easily. "Given that the tax return theft was described in such precise detail, it should be the work of a moment for agents to find out if it actually happened." If it did, it will take a little longer to track down the thieves. But regardless, clearly there is more to this story than is public knowledge. And if it is indeed true, and Romney doesn't pay, we'll know in a few weeks.

Sources: BetaBeat, Business Insider, BuzzFeed, Mashable, Nashville City Paper, Politico, Tennessean, Wall Street Journal

Read more political coverage at The Week's 2012 Election Center.