Meanwhile, Melgen has IRS trouble, too. He has an outstanding IRS lien of $11.1 million for taxes owed from 2006 to 2009

The investigation into his ties with Menendez began in August, after the watchdog group Citizens for Responsibility and Ethics in Washington sent an agent the complaint that “Peter Williams” first sent to CREW months before.

CREW, ABC News the FBI had trouble getting Williams to be forthcoming. He refused to meet with them or speak on the phone.

CREW’s executive director, Melanie Sloan, said Williams was also suspicious because the self-described American citizen and father of two daughters claimed to know about the illicit activity since 2008. But he only complained in an election year when control of the Senate was up for grabs.

The conservative press has championed the mysterious Williams’ cause, noting Menendez has prior legal controversies. He was investigated at one point by former U.S. Attorney Chris Christie, now New Jersey’s Republican governor.

Menendez’s supporters think he’s the victim of dirty tricks from Republicans or the Castro government, opposed to the Cuban-American Democrat’s hardline stance on Cuba.

Melgen’s supporters suggest Williams is a miffed business competitor. And Melgen, according to a noteworthy record of civil litigation as a plaintiff and defendant, has enemies.

Melgen owns a new Hispanic-centric news website, VOXXI, that denounced the “fierce campaign against the dignity of Dr. Salomon Melgen” in an editorial over the weekend.

VOXXI has lavished praise on Menendez. It has also given the kindest of treatment to Menendez friend, Miami Republican Congressman Mario Diaz-Balart. He received $10,000 from Melgen in 2011.

When VOXXI launched a year ago this week, it wrote an article noting that Diaz-Balart introduced Menendez at the website’s launch event “as a ‘giant’ who rallies for the Hispanic community.”

What’s the nature of the congressman’s relationship with Melgen?

“The Congressman is unavailable for comment,” Diaz-Balart’s spokeswoman, Katrina Valdes said in an email. She said he has never travelled with Melgen.

Of the four Miami-area House members who received cash from Melgen, Diaz-Balart is the only one who won’t talk. The others Republican Ileana Ros-Lehtinen, Joe Garcia and Debbie Wasserman Schultz all described their contact with Melgen as limited.

Wasserman Schultz’s office disclosed that Melgen had asked her to get involved with a business issue of his but she declined. He soon stopped giving.

Menendez, however, did advocate for one of Melgen’s companies, ICSSI, which has a mammoth Dominican Republic port-security contract that’s essentially on hold. Menendez spoke about it during a July hearing of the Senate Foreign Relations Subcommittee on the Western Hemisphere. He mentioned it to the State Department, too, and the U.S. Ambassador to the Dominican Republic has taken up the cause of the decade-old case.

Menendez and Melgen supporters say the deal, to X-ray cargo, will help stop the flow of illegal drugs.

And that brings yet another shadowy player into the story: drug lords, who are more than capable of drumming up a few hookers and getting someone to email allegations.

So add them to the cast of possible characters in the drama that includes a Senator, a high-flying donor, prostitutes, Republican dirty tricksters, Cuban spies, and federal agents.

For now, it certainly reads like a mystery novel.

But truth can be stranger than fiction.