Unanswered questions from Trump Jr saga

Now that Hurricane Junior has blown through Washington, special counsel Robert Mueller - charged with investigating possible ties between Russia and the Trump presidential campaign - faces the task of sifting through the debris.

According to CNN, the former FBI director and his team of crack investigators were caught somewhat flat-footed by the recent email revelations. They were believed to have been focusing their attention on former National Security Advisor Michael Flynn, son-in-law Jared Kushner and former campaign chair Paul Manafort, among others.

As it turns out, the first bit of concrete public evidence that someone in the president's inner circle might be open to Russian assistance in the presidential election involved Mr Trump's eldest son.

The president, Trump Jr and his administration have quickly reformed their defences and are now dismissing the meeting with Russian lawyer Natalia Veselnitskaya last June as a minor event during a hurly-burly political season, largely lost in the fog of time, that led to nothing and which they have been admirably "transparent" in discussing.

Key members of Congress seem to think otherwise, with senators like Republican Susan Collins of Maine calling for Trump Jr to be questioned by the Senate Intelligence Committee, and Republican Chuck Grassley of Iowa eager to bring Manafort before his Senate Judiciary Committee.

But while Congress gears up for more hearings, Mr Mueller operates quietly behind the scenes. Where might he look first? What threads, revealed in Trump Jr's emails, will he and his team tug on, to see what unravels?

Here are a few of the tempting questions he might be tempted to ask.

What else did Rob Goldstone think the Russian government was doing to help Mr Trump?

Nestled toward the end of music publicist Goldstone's explosive first email to Trump Jr about the "official documents and information" the Russian government supposedly had about Hillary Clinton was that this constituted just "part of" Russia's support for his father, "helped along by Aras and Emin" Agalarov, the father-son Moscow-based real estate duo.

It's a rather stunning detail for Goldstone to have offhandedly mentioned - and one that Trump Jr, in his "love it" response, seems to have breezed past with no comment.

That kind of remark, however, would cause anyone looking for evidence of a Trump-Russia campaign collusion to stop dead in their tracks and ask: "What's the rest of the story?"

Why is this British guy emailing Trump Jr?

What did Veselnitskaya do next?

Even if one takes Veselnitskaya at her word that she is not an agent of the Russian government and did not know or provide any damaging information about Mrs Clinton to the Trump team during the 9 June meeting, her own recent admissions raise some pressing questions.

On Tuesday she told an NBC interviewer that Trump Jr, Manafort and Kushner may have been "longing for" the dirt on their Democratic opponent.

"They wanted it so badly that they could only hear the thought that they wanted," she said.

Natalia Veselnitskaya went back to Russia with some key information about the Trump campaign

In other words, Veselnitskaya walked out of that meeting in New York with the belief that Mr Trump's campaign both was desperately seeking damaging information about Mrs Clinton and were open to talking to Russian nationals about what they might have to offer.

Given that Veselnitskaya is at the very least a well-connected figure in Moscow, it doesn't require a great leap of faith to think this information eventually made its way to the Russian government. If the US intelligence community is to be believed, that government soon would acquire a trove of damaging information about Mrs Clinton and the Democrats as a result of hacks it co-ordinated into the Democratic National Committee server and the personal email of a senior member of Mrs Clinton's campaign team.

In the ensuing months, details from those hacks would be made public via Wikileaks at times that were particularly damaging to Mrs Clinton.

Derogatory statements about Mrs Clinton's Democratic opponent Bernie Sanders were produced the week before Democrats gathered for their national convention. Transcripts of Mrs Clinton's paid speeches to Goldman Sachs were published just days before the final presidential debate - and cited during that showdown by Mr Trump himself.

The Trump campaign wanted dirt on Mrs Clinton. The Russian government had it in spades. Mr Mueller might want to see if those dots can be connected.

Did Goldstone ever reach out to Rhona?

Another choice tidbit in that first Goldstone email was his suggestion that he might "send this info to your father via Rhona" - a reference to Rhona Graff, the elder Trump's personal assistant.

Graff has served as the gatekeeper to Mr Trump at the Trump organisation - and, according to a profile in Politico, still is the preferred method for the president's business associates to contact him outside of White House channels.

"If I really wanted to whisper something in his ear, I would probably go to Rhona," Trump business associate John Catsimatidis told the publication.

The White House has said that Mr Trump did not know about the meeting with Veselnitskaya - despite the fact that his son, son-in-law and campaign chief were in attendance and it took place in his New York tower.

If this assertion is proven to be inaccurate, Rhona could be the key.

Trump Jr meeting scandal: The key players

What did Emin Agalarov and Trump Jr talk about on 6 June?

The middle portion of the email chain released on Tuesday morning involved Trump Jr and Goldstone trying to set up a phone conversation with Russian pop star/businessman Emin Agalarov.

After a fair bit of wrangling the two apparently spoke, and the very next email was Goldstone informing Trump Jr he was scheduling the meeting with the "Russian government attorney" (Veselnitskaya) for later in the week.

Mr Mueller and congressional investigators may be interested in learning what Agalarov said that convinced Mr Trump to move ahead with the plans for a face-to-face gathering.

And what was the nature of the relationship between Agalarov and the Trump clan, in light of Goldstone's observation that Emin and his father were helping Russia's support of the Trump campaign?

Did Donald Trump Jr break the law?

Donald Trump told a New York crowd in June 2016 he was about to give a "very interesting" speech about Hillary Clinton

What was the story behind Mr Trump's cancelled anti-Clinton speech?

Four days after the first email from Goldstone to Trump Jr about the incriminating information the Russia government was said to have about Mrs Clinton, candidate Trump promised to give a "major speech" the following week discussing "all of the things that have taken place with the Clintons", including Mrs Clinton's alleged misdeeds while serving as secretary of state.

"I think you're going to find it very informative and very, very interesting," he added.

That speech, originally announced for the Monday after the Trump camp's New York meeting with Veselnitskaya, never took place.

Was this an indication that the elder Trump may have known about the meeting - which, according to Trump Jr, did not produce the promised dirt on Mrs Clinton?

That's one more question Mr Mueller might be mulling.

Follow Anthony Zurcher on Twitter.