Terra Nova: “The Sixers”

This show was good, but not great, and one cool aspect was the mysterious Sixers gang that had a secret agenda to overthrow the colony leadership. It was a cool angle, but it turns out the big “mystery” was that they wanted to mine Terra Nova and send the supplies back to modern day Earth. Not much of a surprise, considering the settlers abandoned Earth because it was tapped out and polluted.

Now, the mystery of the “Badlands” seemed like a cool set up from the series finale. But alas, the show was cancelled before the writers had a chance to dig into that one.

Flashforward: The Flashforward

It’s never a good thing when a show gets retooled halfway through its debut season, especially when you’re trying to tweak the mythology along the way. For Flashforwardthe shake-up was more than enough to drive viewers away in droves.

The writers took a pretty cool premise but buried it in a mish-mash of shady characters to try and string it along, which only made things confusing. Not compelling.

Odyssey 5: The Apocalypse

This short-lived Showtime series from 2002 had one of the coolest pilot episodes ever. Seriously. If you haven’t seen it, go watch it. It revolved around a team of astronauts who witness the destruction of the Earth and are sent back in time to stop it. Awesome, right? But that’s when it all goes down hill. Turns out the mysterious extinction of humanity is caused by these lame, AI synthetic baddies that are actually pretty boring antagonists.

Doctor Who: River Song’s identity

The episode “Silence in the Library” introduced the character of River Song, who would go on to be one of the most mysterious characters in modern sci-fi. She’s a mystery wrapped in an enigma, but after a while it just gets too convoluted. Turns out she’s the child of Amy and Rory, who goes on to try and kill/fall in love with the Doctor. A neat twist, sure, but fans were expecting a little more.

Life On Mars: The deep space simulation

It’s hard to blame the writers for this one, because their hand was forced once the network pulled the plug after one season. This U.S. remake of the hit U.K. series about a modern day cop transported to the past was pretty awesome.

But once the writers knew it was over they decided to wrap everything up as quickly as possible with the big reveal that the entire show took place in a spaceship simulation on the way (literally) to Mars. It was better than no ending at all, but seemed to cheapen the experience.

The X-Files: The alien invasion

There aren’t many shows with as many mysteries as this one, and the alien invasion storyline intrigued fans for the shows lengthy run. But it never really got a compelling resolution, and was instead buried in more and more questions. Series creator Chris Carter is still lobbying to make another feature film to close out the show’s greatest mystery of all.

Battlestar Galactica: Starbuck's mysterious return

Yes, the ending was pretty controversial for a lot of reasons, but one of the biggest mysteries left hanging once the ships crashed into the sun was Starbuck. First she seemingly dies, then magically returns in perfect shape driving a Viper that looks like it just rolled off the assembly line.

Ron Moore & Co. were going for ambiguous, and many fans speculate she was some type of angel. But her return played a huge role in the ending of the series, and it just felt hollow to many not to have any definitive resolution after the WTF twist of her return.

Lost: The ending

The grandaddy of them all. One of the most acclaimed series in television history decided to go full-on spiritual after toying with harder sci-fi concepts for the entire run of the show. From smoke monsters to secret scientific study bases and dead characters coming back to life/reappearing in visions, the show had a lot of questions hanging out there for the final season.

As grandiose as it was meant to be, most fans would agree that the big finale in the church was just a massive letdown. Everyone meets up in the afterlife, and it was all about the journey or blah, blah, blah. Fans were holding out for some epic sci-fi answer to the island, and it just didn’t come.

Fringe: Peter is important?

Early seasons set up Peter as being very important to the fate of the universes, and that storyline was essentially paid off when he used the mysterious machine to erase himself from existence and heal the world. But then he came back, and things got somewhat back to normal, and the universes were still pretty much okay. So what was the big deal?

The storyline got pushed even further to the back burner once the show was brought back for a fifth season, which focused on the Observer invasion.

The Event: The Event

When you literally name your series after a big McGuffin, it better be good. The “event” was teased for the entire series run, and it turns out ... the big plan was to bring an alien planet into our solar system. Cool? Sure. Worth the build-up? Not quite.

It could’ve been a cool set up for a second season if the show had been renewed. But it wasn’t, so the big reveal was just a weird twist to close out an uneven show.