When is the show set?
It begins five years before Rogue One: A Star Wars Story, which takes place the same year as Star Wars: A New Hope. An opening title card in Andor notes we're in "BBY 5," meaning five years "before the Battle of Yavin," a.k.a. the destruction of the first Death Star by Luke Skywalker. That also means Andor is set 14 years after Star Wars: Revenge of the Sith, five years after Solo: A Star Wars Story, and four years after Obi-Wan Kenobi.
What's been happening in the galaxy before this?
During the time of Andor, Palpatine has orchestrated the rise of the tyrannical Galactic Empire, which rules the galaxy. The Republic, a democracy, was formerly the galaxy's central government, and its Galactic Senate, located on Coruscant, consisted of elected representatives from planets that were part of the Republic.
Emperor Palpatine was originally one of these senators from Naboo, but little did anyone know he was secretly the Sith Lord Darth Sidious. He was also the puppet master behind the Republic going to war against the Confederacy of Independent Systems, a.k.a. the Separatists, a group of planets that wanted to break away from the Republic due to its corruption. This conflict between the Republic and the Separatists lasted years and was known as the Clone Wars.
But it turned out Palpatine was on both sides of this war, and its real purpose was so he could gain emergency war powers as supreme chancellor and use those powers to reorganize the Republic into the Empire under the guise of restoring security. After the Clone Wars ended with the killing of Separatist leaders Count Dooku and General Grievous, Palpatine had most of the Jedi murdered in Order 66, falsely claiming they tried to overthrow the Republic.
At that point, the Galactic Senate became the Imperial Senate, which no longer had much real power given Palpatine was essentially a dictator. Indeed, Palpatine described the Senate as an "illusion of many voices coming together to govern," when in reality, "there is only one voice. Mine." Palpatine finally dissolves the Senate in A New Hope just before unleashing the Death Star, but it's still around in the time of Andor, and one of the show's main characters is a senator.
During the time of Andor, there exist various cells of rebels fighting against the Empire's tyranny, but they haven't yet united into the organized Rebel Alliance that we see in the original trilogy. That won't happen until about three years after Andor begins.
What do we know about Cassian Andor?
Cassian Andor (Diego Luna) is a rebel intelligence officer when we meet him in Rogue One, which sees him embark on a mission to steal the plans to the Death Star and ultimately die in the process. He was born in 26 BBY, making him 21 when Andor begins, and in Rogue One, he says he's "been in this fight" against the Empire "since I was 6 years old."
According to Rogue One: The Ultimate Visual Guide, Cassian fought against the Republic during the Clone Wars, joining an insurrectionist cell backed by the Separatists. His father was killed during a protest against expanded Republic militarism, the book also says, though this appears to have been tweaked in the show.
At the start of Andor, Cassian hasn't yet joined up with the rebels, so that journey will be depicted in the series. The show will also reveal more about his upbringing via flashbacks to his childhood.
But Cassian tells Jyn Erso in Rogue One she's "not the only one who lost everything," so it's safe to expect plenty of tragedy. We also learn in Rogue One that Cassian isn't afraid to get his hands dirty, as we're introduced to him killing an informant so he can't be captured by the Empire. "We've all done terrible things on behalf of the Rebellion," he says.
What do we know about Mon Mothma?
Despite its title, Andor looks to be an ensemble series focused on various characters crucial to the rebellion's early days, including Senator Mon Mothma (Genevieve O'Reilly), who will become one of the founders of the Rebel Alliance.
Mothma is from the planet Chandrila and by the start of Andor has served in the Senate for nearly 30 years, going back to the days of the Republic. Her parents were both politicians, as her father was arbiter-general in the Republic, while her mom was governor of Chandrila, according to the Rogue One visual guide. During the Clone Wars, Mothma was an ally of Senator Padmé Amidala (Natalie Portman), and they both unsuccessfully fought to cut military spending and negotiate peace with the Separatists.
After Palpatine gains his emergency powers, Mothma is one of the senators who privately sounds the alarm, warning (in a Revenge of the Sith deleted scene) that "as a practical matter, the Senate no longer exists." So Mothma and her fellow senator, Bail Organa (Jimmy Smits), begin making plans to secretly organize a rebellion. They form the Delegation of 2,000, a group of senators who petition (unsuccessfully) for Palpatine to give up his emergency powers. Both Mothma and Bail are arrested, only to declare their loyalty to the Empire and be freed.
By 2 BBY, three years after Andor begins, Mothma resigns from the Senate after publicly accusing Palpatine of ordering a brutal attack on a peaceful world, Ghorman, as depicted in the animated series Star Wars Rebels. This makes her an enemy of the Empire. Mothma explains she's been trying to resist the emperor from the inside while secretly supporting the rebellion, but she has realized "the fight cannot be won in the Senate." So she delivers a speech calling for the galaxy to unite against Palpatine, leading the various rebel cells to come together and form the Rebel Alliance, a.k.a. the Alliance to Restore the Republic. It's possible we'll see these events, and perhaps the Ghorman massacre Mothma was referring to, adapted into live-action in Andor.
By Rogue One, Mothma has become commander-in-chief of the Rebel Alliance. She works with Cassian to gather intelligence about the Death Star but declines to authorize a mission to steal its plans, leading Cassian and the gang to go rogue. As the fighting begins, Mothma and Bail Organa decide now is the time to bring Jedi Master Obi-Wan Kenobi out of hiding, setting the original Star Wars into motion.
Mothma continues serving as rebellion chancellor into the original trilogy, and you'll recall her briefing the rebels in Return of the Jedi, famously saying "many Bothans died to bring us" information about the second Death Star. After the Galactic Civil War ends, Mothma becomes first chancellor of the New Republic, the government that exists by the time of Star Wars: The Force Awakens. With the war over, she moves to demilitarize the Republic, opening the door for the eventual rise of the First Order.
What do we know about Saw Gerrera?
Forest Whitaker also returns in Andor as Saw Gerrera, his resistance fighter character from Rogue One.
Saw grew up on a planet called Onderon, which the Separatists occupied during the Clone Wars, and he formed a group of rebels to fight against them. With secret training from the Jedi, these rebels were able to overthrow the Separatists and return Onderon's king to power, but Saw's sister, Steela, was killed in the fighting. "During this conflict, Saw was captured and tortured by agents of the Separatist king," the Rogue One visual guide explains. "This, coupled with the death of his sister, hardened Saw into a remorseless warrior."
During the Galactic Civil War, Saw led a militant rebellion group, the Partisans, to fight against the Empire. But Saw's actions are considered far too extreme for the Rebel Alliance to officially associate with. He really walks the line between rebel and terrorist, including by torturing prisoners. In Rogue One, it's explained Saw broke with the Rebel Alliance and has been fighting on his own.
"You target civilians, kill those who surrender, break every rule of engagement," Mon Mothma says while berating Saw in Star Wars Rebels, while he argues, "The Empire considers both of us criminals. At least I act like one."
Saw took in Jyn Erso (Felicity Jones) when she was a child after her father was captured by the Empire and forced to build the Death Star, though he later abandoned her.
Fans also may recall that at the end of Solo: A Star Wars Story, Enfys Nest, leader of a group of rebels called the Cloud Riders, says a stockpile of hyperfuel called coaxium is the "blood that brings life to something new … a rebellion." In the novelization, it's explained she delivers this coaxium to Saw Gerrera, showing how different rebels are starting to work together.
What is Preox-Morlana and the Imperial Security Bureau?
Andor introduces a new addition to Star Wars canon: Preox-Morlana, a corporate authority in charge of planets in the Morlana system, including Morlana One. Preox-Morlana has its own security division that can serve warrants and make arrests. Although they report to the Empire, they operate independently. Ferrix, the planet where Cassian is living, is affiliated with Preox-Morlana, and one of its deputy inspectors, Syril Karn (Kyle Soller), grows obsessed with tracking him down.
Soon enough, though, we'll meet the actual Empire when the Imperial Security Bureau enters the scene. This bureau serves as the Empire's intelligence agency and seeks to root out anti-Imperial sentiment in the galaxy. You may recall seeing an ISB colonel, Wullf Yularen, during the Death Star conference room scene in A New Hope, and it wouldn't be surprising if he pops up in Andor.
What will the show lead up to?
The plan is for Andor to be two seasons of 12 episodes each. According to creator Tony Gilroy, it will end five days before Rogue One, meaning the series will span five years. After a three-episode premiere on Sept. 21, new episodes drop weekly through November.