“Timeless", the quasi-cult-classic time-travel procedural had an on-again, off-again relationship with broadcaster NBC, which declined to renew the series after its first season, then changed its mind three days later after vocal social media outcry from fans.

Now, more than a year after the last season aired, “Timeless” returns, and Smithsonian.com is here to help you make sense of it. Did that historical event really happen? Any major goofs? Was that person really like that? Rather than nitpicking we hope that our analyses will deepen your appreciation for the show—and for history.

First, a quick recap of the first season. This’ll contain spoilers, but if you haven’t watched the show yet, this should give you enough background to jump right in with tonight’s episode.

The first season follows the adventures of historian Lucy Preston (played by Abigail Spencer), Army special forces soldier Wyatt Logan (Matt Lanter), and engineer Rufus Carlin (Malcolm Barrett), who are using a time machine built by an Elon Musk-ish figure (Connor Mason, played by Paterson Joseph) to chase a terrorist through time before he can change history for the worse. It’s sort of like “Quantum Leap” meets Where In Time Is Carmen Sandiego?

As the season progresses, the team pursues Garcia Flynn (Goran Višnjić), the terrorist, through time in a spare time machine nicknamed “the Lifeboat,” Mason’s prototype which conveniently seems to work just as well as the stolen one. The good guys pal around with Abraham Lincoln, meet James Bond creator Ian Fleming behind Nazi lines, save the Apollo 11 mission from sabotage (with the help of Katherine Johnson, the heroine of Hidden Figures) and get drunk with Hemingway in Paris. All the while, they’re trying to capture Flynn and prevent him from changing the course of history, although in the altered timeline, outlaw Jesse James is killed by Lucy, not one of his own men; William B. Travis, commander of the Alamo, dies before the historic siege begins; and Abraham Lincoln’s life is almost saved. More disturbing for Lucy, though, is that when she returns back from her first trip through time, the sister she grew up with never existed.

The heroes learn, too, that Flynn is wreaking havoc to destroy a shadowy, Illuminati-type organization called Rittenhouse, which killed his family when Flynn found out that Rittenhouse had been bankrolling Mason Industries’ development of the time machine.

Rittenhouse, we are told, was founded before the United States was even a country by David Rittenhouse—a real historical figure who was the first director of the U.S. Mint, and who was a contemporary of Ben Franklin’s. The real Rittenhouse was also a clockmaker, appropriate for a show on time travel. In “Timeless,” the organization he helped found grows into a menace; it’s implied that many powerful people—mostly men, it seems—are secretly Rittenhouse members. We know that, for example, Thomas Edison, Henry Ford, J. P. Morgan and Charles Lindbergh are members.

As Rittenhouse’s not-very-original plans for world domination unfold, Flynn’s mission of destroying the organization starts to seem less wacky and the heroes add taking down Rittenhouse to their time-travelling agenda. But while Flynn prefers violent means to the end, Lucy and the gang figures out a way to eliminate Rittenhouse in the present without killing anyone or altering the timeline (much). The last season ends on multiple cliffhangers—Flynn is arrested by Homeland Security; Rufus’s girlfriend Jiya is beginning to have mysterious seizures that seem to imply she’s slipping in and out of the timeline, Marty McFly-style; Rittenhouse agents regain control of the time machine; and worst, Lucy learns that her mother is part of Rittenhouse.

That’s about it for Season 1. Overall, the show gets fairly high marks for its historical accuracy; at a panel hosted at the Smithsonian’s History Film Forum last year, the producers noted that they have a historian on staff to avoid making major errors. If anything, my largest quibble with the show is that Lucy’s main skill as a historian seems to be having a near-eidetic memory of dates and names, when— let’s be real—memorizing dates is not actually what history is about. But that’s a minor quibble with an otherwise enjoyable show that seems to relish telling good historical stories.

Now let’s delve into the second season.

It’s clear right away that season 2 is going to be darker and grittier. Rufus, Wyatt, Jiya, Connor and DHS special agent Denise Christopher are holed up in a military bunker after Rittenhouse blew up Mason Industries, killing most of Mason’s other employees. Lucy is forced to take part in a mission to the WWI battlefield—Saint Mihiel, France, on September 14, 1918, to be precise—with her mother and Emma, another Rittenhouse agent. Their mission is to save the life of a soldier named Nicholas Keynes, for reasons not shared with Lucy. Within the first few minutes, Lucy’s forced to kill an innocent soldier to “prove” that she’s loyal to Rittenhouse.

Yikes.

Keynes, meanwhile, is riddled with shrapnel and needs an X-ray. Enter Marie Curie, her daughter Irene, and a mobile X-ray unit!

This is, you may be surprised to read, almost entirely historically accurate. By the time of World War I, x-ray machines were in common use in military hospitals, and Curie and her daughter traveled to these hospitals to deliver equipment and help take the images. As if that wasn’t enough, she invented the first “radiological car,” affectionately nicknamed the “petite Curie,” to take X-rays to the front lines, although there’s no evidence that she was present at Saint Mihiel specifically. She then recruited donors to buy more cars and trained 150 women to operate the machines, which required her to learn to drive (rare for women at the time) and even master car maintenance. She took her daughter along on these missions as well.

Meanwhile, in the present, Wyatt and Rufus embark on a rescue mission after repairing the team Lifeboat. Seems like everyone in this show besides Wyatt has figured out that Wyatt has feelings for Lucy, which is real cute. Wyatt, you’ll get there eventually.

Wyatt and Rufus try to steal a car and get into trouble with some Rittenhouse agents; one has a cell phone, which is obviously odd for 1918. (How was he keeping it charged?) After a quick action scene, they manage to make it to the time machine just as Rittenhouse, Keynes and Lucy show up—along with the Curies, who have noticed that the time machine is giving off a radioactive signature that’s interfering with their x-rays.

Emma wants to kill the Curies now that they’ve seen too much; Lucy’s mother is unsure. But the issue is resolved when Wyatt threatens to kill Keynes if Rittenhouse doesn’t let the Curies and Lucy go. After a quick exchange of prisoners—and Emma threatening to make sure Lucy never gets her sister back—the warring factions get in their respective time machines and return to the present, where we learn that Keynes was a Rittenhouse member who predicted the existence of a time machine—and also Lucy’s great-grandfather.

A few other minor things to note in this episode:

That’s it for this week. Where—and when—will the team go next?