Fringe is back tonight, and there's some stuff you'll probably need to know—or at least need to be reminded about—before the new season starts. We've done our best to compile a Fringe 101 list to help refresh your (and our) memory below.

This is also a "quick start" guide for new viewers. If you think we left something important out, let us know in the comments.

[Warning: Spoilers ahead.]

Walter Bishop has a cow. It's in his lab at Harvard, her name is Jean, and he's delighted about it. He's a genius scientist, who usually solves the mystery at the heart of each episode. He has significant mental crackage, and not just because he was in a mental institution for years. He worked on a portal to an alternate universe and even took his son Peter from it.

Peter Bishop has a murky, off-the-radar past. Turns out he died as a boy in this, our universe. Walter, heartbroken, replaced him with the boy Peter from the alternate universe, who is the Peter we have come to know and love. It's unclear at this point what happened to alternate-universe Walter.

OK, let's talk about this alternate universe. It's the mainspring of Fringe—not time travel, not faster-than-light travel, but alternate universes. In the not-our-universe once inhabited by the alternate Peter who is now in our universe, John F. Kennedy is alive and aged, Len Bias didn't die of cocaine, and the World Trade Center towers are standing proud and gleaming.

There is a bald guy who is in every episode, mostly briefly. He's usually around when something significant happens. He and Walter know each other. He's called The Observer. I tend to think of him as the eternal bald observer, because a fair amount of this kind of science fiction has a bald observer.

Are there any crimes going on here? Yes, of course, but I wanted to tell you about the cow first. Olivia Dunham is an agent on a special FBI team tasked with investigating strange deaths and the like. In this, Fringe is a successor to The X-Files. But some crimes—especially those involving teleportation—connect to the alternate universes. They also connect to Olivia, who realizes she was treated as a child with a special drug. Indeed, she was experimented upon by Walter.

A little more about teleportation—when was the last time you saw it in a contemporary television series? You've of course seen it in Star Trek beaming, but the teleportation in Fringe is more ragged around the edges, more desperate, and feels more like the novel The Stars My Destination (highly recommended, by the way).

Olivia has enlisted Walter and Peter to help. She and Peter haven't hooked up yet, but I'd say it's just a matter of time. Broyles is the head of her team—you'll recognize the distinctive actor, Lance Reddick, from The Wire and Lost. The team has some good guys and bad guys—a lot more interesting than the FBI team from Numb3rs.

Olivia's former lover was her former FBI partner, John Scott. He's former in both pursuits because he's dead. Walter had a way of getting Olivia into his dead mind. But it was too dangerous for her, so they stopped that, and it's not clear what role, if any, John will play in the second season. Just keeping you posted in case he does come back (though the actor has moved on to another series), or in case you wanted to know.

Charlie is Olivia's current partner, and they're just good friends.

Astrid's also FBI and works in the lab with Walter and the cow.

Olivia's sister and beloved little niece live with her. The sister seems to like Peter, but they are mostly there as vulnerabilities that Olivia's deadly opponents can exploit.

And make sure you keep an eye on the glyphs—leaves, half apples, seahorses, and the like—on the screen when Fringe breaks for commercials. The glyphs provide clues. Some of them have been decoded on the Web.

And who are Olivia's opponents? Who are the ultimate villains in Fringe? Again, not completely clear. But William Bell, played by Leonard Nimoy, is the genius scientist who used to work with Walter. Bell now straddles both universes as head of the mysterious, powerful, Massive Dynamic. He also has some connection to ZFT (Zerstorung durch Fortschritte der Technologie, or destruction through the advancement of technology), the terrorist group that's behind the crimes, which may have been founded either by Bell or Walter.

And then there's Nina Sharp, played by Blair Brown, who's Bell's chief assistant. She's the current head of the company in our universe, and knows a lot more than she lets on.

The last scene of the last show of the first season found Olivia—our Olivia—in Bell's office, with Bell, in the alternate universe, in his Massive Dynamic office, in the South Tower of the World Trade Center, 2009.

Paul Levinson, Ph.D., is professor of communication and media studies at Fordham University in New York City. His eight nonfiction books include The Soft Edge (1997), Digital McLuhan (1999), Realspace (2003) and Cellphone (2004). New New Media, exploring blogging, Twitter, YouTube and other "new new" modes of communication, will be published by Penguin Academics in the summer of 2009. His science fiction novels include The Silk Code (1999, winner of the Locus Award for Best First Novel), Borrowed Tides (2001), The Consciousness Plague (2002), The Pixel Eye (2003) and The Plot To Save Socrates (2006). His short stories have been nominated for Nebula, Hugo, Edgar and Sturgeon Awards. He reviews the best of television in his InfiniteRegress.tv blog and was listed in The Chronicle of Higher Education's "Top 10 Academic Twitterers" in 2009.