It's an apropos plot device because it gives the player a high level goal that's easy to grasp while staying true to the DS9 world. The Fallen follows the adventure of Captain Benjamin Sisko and crew as they pursue the Orbs. Their efforts will take them to numerous locales, from the familiar decks of the DS9 space station and the bridge of the USS Defiant, to a bleak prison planet, forgotten ruins on Bajor, secret research facilities, and more. There are roughly 10 levels across more than 30 maps built using a modified Unreal Tournament engine.
The attention to Trek detail is outstanding. Although the levels tend to be on the dark side, this certainly matches the look of the show, and the textures and architecture are faithful to the series. Major characters from the show are here, some voiced by the real actors. The characters have a good likeness to their actor counterparts, and objects in the game like ships, weapons, and costumes are right off the set. Seeing Jem 'Hadar soldiers charge you as they decloak is pretty awesome. The effort extends to the sound effects, with authentic weapon reports, transporter and tricorder noises, and voices of the different races. Even the music is familiar.
The story told in The Fallen is simple, but the path it takes also recalls its television inspiration. Players can play the game from the three perspectives of characters from the show: Sisko, Worf, or Kira. It's worth playing each character, since each will see different levels as they progress on parallel courses. This meant more work for the developers, but it's a nice move that adds play value. It further builds an association with the show, which often took an ensemble approach.
Again, having no idea what a DS9 is doesn't mean you can't play The Fallen. Although it tries to be an action adventure hybrid, it's heavily skewed toward action, which doesn't take Trek knowledge to figure out. The level design is clean, and balances the need to be linear enough to keep the story going, while allowing for the players to explore at their own pace. Extracurricular exploration isn't necessary, but there are rewards for those that do it. There are a few platform jumping exercises, but not so many that you'll shut the game down in a flurry of curses.