Here is the concept I am working on at the moment for my UA game.
The Long Way Home
My name is Janus Smithfire. An adventureer. I got flipped through a portal to a distant part of the spheres. I'm being hunted by an insane milita commander. Can anyone hear me? I'm just trying to find a way home.
It is a grab bag of elements, mainly from Farscape (Characters thrown in a world they do not understand) and Alias (Shadow agency, prophecies and artefacts).
Department 7 is the SD6 of the world. They have followed clues found in a number of ancient locales / writings and discovered the remains of an orrery hidden in a long abandoned complex in the swiss alps (codenamed 'The Planetarium'). This orrery can be used to predict the opening of the shadow portals, although at the moment it is not very accurate as parts of orrery as missing (at least 4 crystal spheres and 3 gear seactions). Technicians have been trying to develop computer programs to fill in the blanks.
D7 has agents keeping watch for strange occurances to match up with the orrery predictions. The plan is to capture for study whatever comes through the portals for it's own gain.
The players are a group of adventureers wash up on these modern shores, barley managing to evade capture, discovered by a Shdowkind Underground Railway. They find out that they have a limited time before their memories disappear (year and a day). The Railway knows of the orrery and they also have some information that D7 does not know about; a replacement gear. When this gear is placed in the correct position, and the orrery is complete, it can be used to predict portals that run back to the Shadowlands and a way home.
The race is on.
Eventually I'll have about 12 linked adventures (when I get round to it), 8 about gaining parts of the orrery and dealing with other events including the finally confrontation. Each adventure will cover a month of game time.