If 2016 was the bravura opener and 2017 the tension-building second act, 2018 could deliver an action-packed conclusion to the Russia imbroglio.

Or this story might still be getting started.

Even without knowing every surprise the saga might bring in the new year, there are already enough waypoints on the calendar to confirm that 2018 will ratchet up the volume yet again.

Here are four big storylines to watch.

Russian President Vladimir Putin says an explosion at a St. Petersburg supermarket on Wednesday was a terrorist act, and that another attack in the city had been foiled by the country's security service.

A bomb went off in a branch of the Perekrestok supermarket, wounding at least 13 shoppers in Putin's hometown, Reuters reports:

Russia hosted the last Winter Olympics, in 2014. But the country is banned from being represented at the 2018 Games that start in February, after the International Olympic Committee said it found a widespread culture of Russian cheating through performance-enhancing drugs.

The International Olympic Committee has suspended the Russian Olympic Committee "with immediate effect," essentially banning the country from the upcoming Winter Olympics over Russia's system of state-supported cheating by athletes using performance-enhancing drugs.

Russian athletes can compete in the 2018 Games in Pyeongchang, South Korea, the IOC said Tuesday — but the athletes will have to pass strict scrutiny, and instead of wearing their nation's uniform, they will compete under the title "Olympic Athlete from Russia (OAR)."

Updated at 4:08 p.m. ET

Justice Department special counsel Robert Mueller has reportedly subpoenaed Trump family financial records from the German financial giant Deutsche Bank, a move that could signal a major new direction for his inquiry.

Updated 12/2, 11:47 a.m. ET

President Trump's first national security adviser, Michael Flynn, pleaded guilty Friday to lying to the FBI about his contacts with the Russian ambassador during the transition, and he is cooperating with the special counsel's investigation into Moscow's interference in last year's election.

Flynn told investigators that he was instructed to engage with the Russians by senior members of the Trump transition team.

AK Rockefeller / flickr creative commons

Mistrust of the government's version of the facts... Paranoid conspiracy theories... Allegations of treason... Distrust of American institutions... Controversial governmental investigations...

You might say that America's modern era started 54 years ago today in Dallas.

Enrique Dans / Creative Commons

The prospect of nuclear war. How serious is it?

This hour, Australian anti-nuclear activist and writer Dr. Helen Caldicott shares her answer to that question.

We also check in with experts from the Cato Institute and UConn. And we want to hear from you. 

The law intended to shine a light on foreign entities and foreign governments working to influence policy in Washington, D.C., has been called everything from "toothless" to "a complete joke."

But Justice Department special counsel Robert Mueller isn't laughing — and neither may potential violators if he decides to make it his new weapon of choice.

Special counsel Robert Mueller's investigation has entered the West Wing.

Mueller's team is charged with looking into whether anyone on President Trump's campaign worked with the Russians who attacked the 2016 election, so it was inevitable that investigators would want to talk with aides now working in the White House.

Some, like top adviser and son-in-law Jared Kushner, communications director Hope Hicks and policy adviser Stephen Miller, were key players in the campaign as well.

Gage Skidmore / Creative Commons

Attorney General - and former Senator - Jeff Sessions has spent more time on Capitol Hill than he’d like over the last few months, again facing tough questioning about what he did and didn’t know about contacts between Russia and the Trump campaign he was a part of. 

Updated at 6:25 p.m. ET

Attorney General Jeff Sessions told the House Judiciary Committee Tuesday that his "story has never changed" about his and other Trump campaign officials' connections to Russia.

"I will not accept, and reject accusations that I have ever lied," Sessions said. "That is a lie!"

C Watts / flickr creative commons

In 1959, Soviet geneticist Dmitri Belyaev started an ambitious experiment to study the origins of domestication -- he would attempt to breed domesticated wild foxes by selecting on their behavior alone, a process he imagined our ancestors carried out with dogs thousands of years before.

Updated at 10:30 a.m. ET

During the 2016 presidential campaign, Donald Trump Jr. was in direct contact with WikiLeaks at the same time the muckraking website was publishing hacked emails from Democratic officials that proved damaging to the Clinton campaign, according to several major publications.

Following the reports, Trump Jr. acknowledged the contact in a tweet detailing one exchange with the radical transparency organization.

Cheburashkina_Svetlana / Flickr Creative Commons

This year marks an important milestone in Russian history -- the 100th anniversary of the 1917 Russian Revolution.