I'm sure you all remember the heart-wrenching first season of episode of Heroes where Hiro realized that, even though he could travel back in time, he still couldn't prevent the death of his girlfriend Charlie, because somethings are just destined to happen. You cried, I cried and we all missed the real lesson of the episode: Hiro is a moron. After all, if there's one thing that Heroes is actually about, it's messing about in time to fix whatever problem is affecting future New York that particular week. Join us as we look at what's to come - and what was to come, before other things started to come instead - in NBC's superhero soap opera, thanks to those meddling kids.The mechanics of time travel is something that the writers of Heroes seem to have spent some time really thinking about, given the various ways in which they've used it throughout the show. We've seen people who can paint the future (Something that four separate people have done so far on the show, to varying degrees of success - although it's maybe worth noting that only Isaac has a 100% accuracy rate, perhaps because everyone was better at forward planning in the first season), we've visited the future - well, futures - and we've even visited the past a few times, as well. But that doesn't necessarily mean that the laws of time travel on the show are entirely consistent. Fans may argue about whether or not Hiro did change time when he tried to save Charlie, but the writers seemed to be fairly clear that the main events had stayed the same: Charlie still died, Sylar still had her powers afterwards, and Hiro decided that he couldn't change history (Even though he actually already had, by that point). But then, how do you explain the show's multiple futures? By our count, Heroes has had somewhere between four and six different "futures" that we've actually seen for ourselves - the oracular painters' visions don't count, because people with no irises scare us - and most of those have been undone by the characters changing that future's history based on foreknowledge of what was to come:

Future 1: New York gets blown up in a nuclear explosion caused by Sylar one year in the future, as seen when Hiro saw when he first discovered his powers in "Don't Look Back," the show's second episode (The cause of the explosion is revealed in "Five Years Gone," later in the season). Undone because: Peter saved the cheerleader, but didn't save the world. Of course, what caused him to save the cheerleader? Hiro time-traveling and telling him to do it.

Future 2: New York gets blown up in a nuclear explosion caused by Peter one year in the future, as a result of Peter saving the cheerleader because Hiro told him to. Bad move, Peter. Everyone has gone bad as a result - well, except for Ando, who died in the explosion: Hiro has become a ninja, Nathan has become President and Ali Larter has become a stripper because the writers like to imagine her naked. We saw all of this in "Five Years Gone" in the first season. Undone because: Nathan flew Peter into the "high-enough-that-a-nuclear-explosion-is-apparently-meaningless-sphere" at the end of the first season. It's unclear why this didn't happen in the Five Years Gone timeline, other than the promise of cheap drama, so this may not have changed as a direct result of time travel (although Hiro's time-traveling antics probably helped, let's face it). Possibly not undone because: See Future 4a. No, really.

Future 3: 93% of humanity has died as a result of the Shanti Virus, which was a plot device if ever there was one. We see this in "Out of Time," during the second season of the show that we all try to forget ever existed as completely as Peter has forgotten Caitlin, his Irish girlfriend that he accidentally abandoned there. Oops. Undone because: The virus didn't get released after all at the end of "Powerless," the last episode of the second season, thanks to Peter knowing what would happen if it did, thanks to time travel. So what happened to Caitlin? No-one knows, not even the writers, who've complained that their heads spin when they try and work it out. Future 3b: This future definitely doesn't exist but in some strange fan-fiction somewhere, but as originally shot, the Shanti Virus did get released at the end of "Powerless," and the never-completed later episodes of that season would have included Peter's attempts to rescue Caitlin and a town quarantined because of the virus. Undone because: It never really happened in the first place.

Future 4a: Four years from now - although when "now" is seems to be a somewhat elastic concept; I think it's actually somewhere around the end of 2007 at best, but "four years" forward brings us to the same time period as "Five Years Gone"'s Future 2, which may be important - future Claire tries to shoot future Peter, because she blames him for the way everything has turned out. It all happened at the start of "The Second Coming" from the third season. Potentially meaningful point: Both Claire and Peter look exactly like they did in Future 2, whether it's hair color or massive scar on face and stubble. Are the hair and make-up people that lazy, or is there some connection between the apparently undone "Five Years Gone" flashforward to this time period Undone because: Future Peter shoots present Nathan, thereby stopping him from revealing the existence of superhumans publicly, which was what caused all the problems, apparently. Time travel saves the day again! Except, maybe not. See below.

Future 4b: Hiro travels to some unspecified point in the future where he is fighting Ando, who now has superpowers - and he's not the only one - before there's a massive explosion that's very similar to the McGuffin behind the first season. But Claire's not a cheerleader anymore! How can they stop this one? Again, from "The Second Coming." Undone because: Well, it's not, yet.

Future 4c: Again at some unspecified time in the future, all of the regular characters on the show have been killed by escaped villain Knox, escaped Alias actor Adam Monroe, Matt's telepathic absent father, some Ali Larter character that may or may not be Tracy Strauss (and really who cares that much anymore?) and potentially Sylar. This may or may not have been a true future - We saw it at the start of "The Butterfly Effect" in the third season, but it was Angela Petrelli's dream, and even though she's one of the show's many oracular characters, it was a dream. Undone because: We don't even know if it's real yet, never mind how to undo it. The problem with these last three futures - besides the feeling that we've seen them before (perhaps literally, given the crossover between "Five Years Gone" and "The Second Coming") - comes not from the show itself, but from an interview with writers Aron Coliete and Joe Pokaski, who said that not only wasn't future 4a changed by Nathan's shooting, but that "[t]hese are in fact, all the same future." Wait - didn't we see Hiro get killed in two entirely different ways in two of them (Zapped by Ando and then stabbed by a sword, respectively)? How does that work? Tomorrow's episode of the show, "I Am Become Death," promises to either address some of this confusion or increase it, as FuturePeter and PresentPeter travel to a/the future and, let's face it, probably see Hiro die in yet another way just for shits and giggles just to mess with our heads. So exactly how does time travel work on Heroes? After literally minutes of consideration, the best we can work out - ignoring the always present possibility of "it does whatever the writers need it to at that moment, internal logic be damned" - is this: You can change the details, but not the ultimate outcome, of destiny (or Peter Petrelli's unfortunate shaving accident, it seems) through time travel. Charlie will still die; she'll just have met Hiro six months earlier and been happier. There will always be a legend of Takezo Kensei, but he may end up being Hiro instead of a refugee from a JJ Abrams spy drama... and no matter how many cheerleaders you save or viruses you stop crashing against a vault floor, the future of Earth Heroes will always be dystopian, New York-centric and in need of the kind of help that only comes from the Peacock Network. If true - and it's something that makes the similarities in Future Claire and Future Peter's appearance between "Five Years Gone" and "The Second Coming" - then it presents a couple of problems for the writers of the show. Firstly, it suggests that we're probably going to continually have some level of time-travel or change-the-future plotline throughout the entire series, never mind the entire season, and secondly, it kills a lot of the dramatic tension if we find out that no matter what the characters do, we're still all going to end up completely screwed by 2011. Have the writers written themselves into a corner, or will we end up seeing the rules of Heroes time travel clearly explained in such a way as to allow for a non-gloomy future sooner rather that later? Only time, ironically, will tell. Just let me know if I end up having to be get my Shanti innoculation.