President Trump spoke at a news conference in Paris on July 13 and defended Donald Trump Jr.'s meeting with a Russian lawyer. (The Washington Post)

In this occasional series, we will bring you up to speed on the biggest national security stories of the week.

Another bombshell in the growing scandal surrounding President Trump and Russia landed early this week. On Tuesday, the president’s son Donald Trump Jr. released an email exchange with him and and a publicist who told him that a Russian lawyer could provide the Trump campaign with potentially damaging information about Hillary Clinton that was “part of Russia and its government’s support for Mr. Trump.”

The New York Times first reported over the weekend that Trump Jr. met with Natalia Veselnitskaya, a Russian lawyer, at Trump Tower in 2016. Then-campaign manager Paul Manafort and Trump’s son-in-law, Jared Kushner, were present, as well. The president has defended his son, calling him a “wonderful young man” and a “good boy.”

Here is everything you need to know about this fast-moving story:

Who are the new key players?

— Rob Goldstone, a British music publicist for Russian pop star Emin Agalarov. Goldstone is encouraged by Agalarov to arrange a meeting between the Russian lawyer and Trump Jr., according to the emails. He sends an email to Trump Jr. in June 2016 saying that the information the Russian lawyer could provide would be interesting to Trump. The exact line in his email reads: “This is obviously very high level and sensitive information but is part of Russia and its government’s support for Mr. Trump.”

— Natalia Veselnitskaya, a Russian lawyer. Veselnitskaya was first described in Goldstone’s email as a “Russian government lawyer.” Although Veselnitskaya worked in a local prosecutor’s office in Russia, she said she does not work for the Kremlin. In an interview with The Washington Post, Veselnitskaya defended herself by saying no one tasked her with meeting Trump Jr. and that the story is “nonsense.” She has also advocated for lifting economic sanctions against Russia imposed by Congress. The Kremlin has denied knowing her.

— Emin Agalarov, the Russian pop star, son of real estate developer Aras Agalarov. The Agalarovs first met Trump in 2013, when they helped Trump bring the Miss Universe pageant to Moscow. Trump even appeared in one of the music videos by the younger Agalarov. His father tried to set up a meeting with Russian President Vladimir Putin and Trump, but it never transpired.

What was actually discussed in the meeting?

Trump Jr. said the meeting with the Russian lawyer didn’t result in anything useful.

In his official statement concerning the meeting, Trump Jr. said Veselnitskaya made “no sense” and that she changed the topic to discuss the American adoptions of Russians and the Magnitsky Act, the piece of U.S. legislation she has been working to overturn. The law is seen as the first gateway to lift what Moscow considers are punishing U.S. sanctions placed on Russia for its intervention in Ukraine.

Veselnitskaya told The Post that even from the start of the meeting, “it was clear we were talking about two different things.” In all, Trump said the meeting lasted about 20 to 30 minutes.

So why is this a big deal? 

After months of speculation whether the Trump campaign colluded with Russia to win the presidential race, the emails offer a stark example of the campaign seeming eager to receive information from the Kremlin about its political opponent.

Most ethics lawyers agree that it is very unusual that a foreign government would provide this kind of information on a rival candidate.

Typically, the research comes from scrubbing public records and legislative histories.

Did Trump Jr. break the law?

Not necessarily, because it depends whether what Trump was offered would be considered “a thing of value.” U.S. law states it is illegal for campaigns to solicit or accept contributions from foreign nationals or foreign governments. The Post's David A. Fahrenthold explains: “What Trump Jr. was offered might be considered a ‘thing of value,’ if the information he was seeking had cost someone money to produce — or if it was something that a campaign might have paid for.”

Trump Jr. maintains his meeting did not produce any value.

What could Trump Jr. have done instead?

Some say the campaign should have called the FBI. During the 2000 presidential debate, Vice President Al Gore’s staff received a package containing stolen materials from George W. Bush’s campaign. The Gore campaign contacted the bureau.