Dark Matter returns to Apple TV next week. The first season followed Blake Crouchâs acclaimed sci-fi novel very closely, so what lies ahead is uncharted territory for the series. But we can guess there will be more freaky physicsâthe show is about interdimensional travel, after allâand characters encountering alternate versions of each other as well as themselves.

Given Dark Matterâs high-concept, layered set-up, a crash course is in order even if you watched season one. With that in mind, hereâs everything you need to know about Dark Matter ahead of season two.

What is Dark Matter about?

Dark Matter is based on Blake Crouchâs 2016 novel of the same name; the author created the Apple TV series. Heâs also its showrunner, one of its executive producers, and co-wrote or wrote six out of season oneâs nine episodes.

The story follows Jason Dessen, a Chicago physics professor whoâs got a pretty good lifeâheâs married to Daniela, the love of his life, and they have a 16-year-old son, Charlie.

But he canât shake the feeling that perhaps heâs missing out. He gave up a cutting-edge career and took up teaching when Daniela got pregnant, choosing a less intellectually fulfilling but more family-oriented path instead. His nagging sense of regret balloons when his best friend and former colleague, Ryan Holder, wins a prestigious award for his work.

As Jason trudges home from Ryanâs celebration, nursing sad-sack âwhat if?â thoughts, everything changes. Heâs kidnapped by a masked man, drugged, and dragged into a strange cube. He wakes up groggy and surrounded by people whom he doesnât know but who all seem to know him.

We soon come to understand that Jasonâour Jason, or Jason #1âhas unwittingly swapped lives with the Jason from this world, aka Jason #2.

Jason #2 decided to break things off with Daniela when they realized she was pregnant. Instead, heâs spent the past 16-plus years focusing all his passion and energy into building that strange cube, which everyone on Dark Matter calls the Box.

But just like Jason #1, Jason #2 started having some regrets about his choices. So he used his invention, which he constructed thanks to a company called Velocityâwhich is run by his extremely wealthy former college pal, Leighton Vanceâto find a Jason whoâd built a life with Daniela and appropriated that life for himself.

Once that premise is established, Dark Matter follows Jason #1 as he attempts to use the box to find his way home, accompanied by Velocity staff psychiatrist Amanda Lucas, whoâd been dating Jason #2 in their world. Thereâs a ticking clock at play since box travelers use a specially made drug to enable their minds to comprehend multiple dimensions, and the pair has only a limited supply.

In the parallel storyline, we watch as Daniela starts to pick up on the weird changes in her husband, who looks identical but has some unwelcome new personality quirks. Heâs also lacking some important memories and knowledge, like the fact that Charlie has a dangerous nut allergy. And despite the fact that Jason #2 engineered the switch specifically so he could have Jason #1âs simpler life, it soon becomes apparent he canât put aside his obsession with the Box, and it remains his focus in this dimension too.

What is the Box and how does it work?

Dark Matter carefully walks the line between âthis is actual scienceâ and âthis is outright sci-fiâ by making the Box feel like something that could be real, even if it had to come from a more technologically advanced universe. And it doesnât spend too much time explaining beyond the basics. All the viewer needs to know is that travelers go in the box, take a special mind-expanding drug, and then a corridor filled with doors appears, each one leading to a different dimension.

Aside from the know-it-all Jason #2, Dark Matterâs characters are learning about the Box along with the audience, so we get to see their trial-and-error process as they come to understand more about it.

The Box always has the same GPS coordinates in every world, but the things around it inevitably change. Sometimes itâs in an open field; sometimes itâs inside another building. A âbox pilotâ can only access a world they could have been born into, where they existed or still exist. So itâs not like Rick and Morty, where the characters visit completely alien places. Itâs always a ânext-doorâ version of Chicago. Some are wildly different, having succumbed to disasters (blizzards, floods, a deadly plague), while others are just slightly âoffâ with eerie nuancesâlike the world where Jason #1 realizes almost too late that the version of him there is in jail for some unknown but terrible offense.

Navigating the Box proves to be Jason #1’s and Amanda #2âs biggest challenge. It responds to the userâs mental state, so you have to be in just the right mindset before you open each door. If youâre stressed or angry, youâll find the landscape version of that on the other side. You have to clear your mind and concentrate on a positive outcome, which proves trickier than it sounds, especially as Jason #1 becomes more frantic trying to get back to his point of origin.

Who are the main characters on Dark Matter?

Jason Dessen (Joel Edgerton) – Jason #1 is a physics professor who gets kidnapped out of his world by Jason #2, inventor of the Box. Theyâre ostensibly the same guy, sure, but Jason #1 is the reluctant hero you root forâwhile Jason #2 is the villain you absolutely root against.

Daniela Dessen (Jennifer Connelly) – Daniela #1 is an artist turned gallerist whose suspicions about Jason #2 grow across the season. We do meet other versions of Daniela across the dimensions (in some sheâs a successful artist, and in others, sheâs a blonde), but Daniela #1 is who we mainly spend time with.

Charlie Dessen (Oakes Fegley) – Charlie #1 is Jason and Danielaâs 16-year-old son. He had an identical twin named Max who died after a childhood illness; as part of Jasonâs travels, he visits a world where Max is still alive. One of the biggest weak points in Jason #2âs facade is that he doesnât know the Dessen family traditions around honoring Max on the twinsâ birthday.

Amanda Lucas (Alice Braga) – Dark Matterâs main version of her is Amanda #2. Sheâs a psychiatrist who works at Velocity and decides to help Jason #1 find his way home, partially because she has a romantic history with Jason #2, but also because she realizes Velocity security will kill her if she sticks around because she knows too much.

Ryan Holder (Jimmi Simpson) – We meet three versions of Ryan: Ryan #1 is Jason #1âs best friend and a brilliant chemist. Ryan #2 is no less brilliant but less successful in his career. Both of these Ryans create versions of the purple-hued drug used to allow the human brain to accept superposition while in the Box, which makes him valuable to anyone else who wants or needs to travel.

Ryan #3, meanwhile, is an auto mechanic who is very confused when Jason #2 kidnaps him and uses him to replace Ryan #1. Turns out Ryan #1 asks too many questions, so Jason #2 strands him in yet another world for his troubles. That’s a more benevolent fate than Ryan #2 gets; he’s killed by Velocityâs ruthless security team.

Leighton Vance (Dayo Okeniyi) – Season one focuses on Leighton #1, whoâs grown bored of his luxurious existence living off a trust fund provided by Velocity, the family business. So he gets very excited when his old college pal (Jason #2, posing as Jason #1) shows him what the Box is capable of. Leighton agrees to give Jason millions if Jason will supply him with ampules of the drug so he can do his own wandering.

Leighton #2, who funded Jason #2âs invention in their shared world, chases after Jason #1 and Amanda #2 when they flee in the box; itâs implied he may have perished after taking one too many wrong turns.

Blair Caplan (Amanda Brugel) – Blair #1 is an attorney and Danielaâs no-nonsense best friend; itâs thanks to her that Daniela acts on her suspicions about Jason #2 not being who he says he is. Meanwhile, Blair #2 is a Velocity scientist who volunteers to be the first person to travel in the Box. She ends up in a world ravaged by murder hornets; security camera footage of the Box reveals that the swarm originated when another version of Blair brought them through the Box with her.

Jason #1 and Amanda #2 stumble into her dangerous world along the way and try to convince her to leave, but sheâs not ready to get back in the Box. She does have some sage advice for Amanda, though, encouraging her to prioritize her own life rather than spend it helping Jason get back to his world.

Where did season one of Dark Matter leave off?

In the final two episodes of Dark Matter season one, Jasons #1 and #2 realized they werenât the only Jasons running around Jason #1âs version of Chicago. It seems every choice Jason #1 made during his time in the Box spawned variants who are very nearly exact copies of himâthey branched off from him after he was kidnapped by Jason #2. All of them are trying to get back âhomeâ to Jason #1âs world. Each believes he is the most worthy of reclaiming a place there. They all want the same thing because… theyâre basically the same guy.

But Daniela and Charlie realize theyâve found the right Jason #1âthe character weâve been following throughout Dark Matterâand after some running, hiding, and no shortage of violence that eliminates several of those Jason #1 variants, the OG Dessen trio make their way to the Box, aided by a getaway car and stash of drug ampules handed over by a repentant Jason #2. A crowd of Jasons awaits them at the Box, but they stand aside and let the family through.

The season ends on the optimistic thought that together, theyâll find a new world where they can restart their lives together, unbothered by envious duplicates.

Elsewhere on Dark Matter, Amanda #2, who spent a lot of time traveling the dimensional highways with Jason #1, remained in that peaceful, cheerfully progressive world, though we see she’s moved from Chicago to Seattle, as she told Jason she would. This is the same world where Jason #2 abandoned Ryan #1.

Ryan is trying to recreate the purple-hued drug in this new world. We also see him, Space Needle in the background, approaching a surprised Amanda. He says he doesn’t know her, but he’s been looking for her.

Leighton #1âa happier, groovier version of the character than the vengeful Leighton #2âis seen to still be on his journey through the multiverse. And Blair #2 finally gets the courage to leave the murder-hornet-infested world where sheâd been hunkered down for far too long.

What is season two of Dark Matter about?

Hereâs what Apple TV has released: âSeason two picks up with the Dessens as they settle into a quiet life in a world that finally seems safe until the unimaginable forces them to run once again. As Jasonâs obsession with the Box deepens, Danielaâs (Connelly) growing paranoia pushes her to the brink, and their son Charlie (Fegley) starves for a sense of stability as their family is threatened.

Elsewhere, Amanda (Braga) and Ryan (Simpson) join forces in a desperate attempt to find their way home. With Blair (Brugel) determined to stop him, Leighton (Okeniyi) relentlessly chases his grand vision of creating a perfect world.â

We also suspect all those dead Jasons scattered around Jason #1âs original world, where Jason #2 is presumably still lurking, will attract someoneâs attention. All those returning cast members will be joined by new faces played by Margo Martindale and Chris Diamantopoulos, though we donât know anything about their characters.

Apple TV also shared a season two trailer that offers a few clues:

Weâll be staying the hell away from tornado-infested Chicago, thank you very much. Dark Matter returns to Apple TV for its 10-episode second season starting August 28.

Want more io9 news? Check out when to expect the latest Marvel, Star Wars, and Star Trek releases, whatâs next for the DC Universe on film and TV, and everything you need to know about the future of Doctor Who.