Story arcs have always been one of my weak points as a gamemaster. My ability to create interesting antagonists and exciting situations has gotten me through a lot of games, but my campaigns tend to be very episodic with little overall plot. With that in mind, I want to try my hand at planning the skeleton of a story out now and see what meat I can put onto it later.
I'm starting the way all good RPG stories do, by plagiarizing everything within arms reach. Since I'm aiming for a plot that is both goal-oriented and character-driven, I'm borrowing heavily from computer RPGs in the vein of Deus Ex and Vampire: the Masquerade: Bloodlines.
Urban Fantasy borrowing heavily from D20 Modern's Urban Arcana and White Wolf's World of Darkness. Magic exists but is unknown to the common populace, protected by both an enforced conspiracy and inherently selective perception. Those who are aware of magic and supernatural creatures are considered "awakened."
The PCs are caught in the middle of a three-way fight over a macguffin. Two of the factions present a moral choice between order and chaos. The third faction are one-dimensional antagonists to be fought without guilt.
Victor - Local magistrate and chessmaster. Organized businessman/politician type. The PCs start in his employ. He is highly ambitious, but acts within the law and rewards loyalty well.
Janis - The PC's contact with those who oppose the magistrate's rule. 30-something street punk. Well intentioned and very anti-establishment. May become leader of the opposition if the PCs support her.
Roy - Runs a local bar with an awakened-only VIP room. A good source of friendship and information for the PCs, being one of the few major characters without an agenda.
Sariah - Knight Templar leader of the Hunters. Believes that all magic users and supernatural creatures serve Satan and must be exterminated. A primary antagonist throughout, and penultimate boss battle.
Six Session Breakdown
1) The PCs owe Victor a favor, and he's calling it in. He's heard stories of something big going down, and sends the PCs on a mission to find out what it is. The PCs recieve help from Roy, encounter the hunters, and uncover the existence of the macguffin. Victor tells them that if they bring him the macguffin, their debt to him will be more than repayed.
2) Victor sends the PCs on another macguffin-related mission. The encounter Janis, who warns them not to trust Victor and asks them to help her and the opposition. PCs can take any course of action without major consequences.
3) PCs get a mission where they will have to make a major choice between Victor and the opposition in the fight over the macguffin. Whatever they do, the balance of power will be upset.
4) Shit gets real. As Victor and the opposition fight openly, the hunters become a real threat with the arrival of Sariah. She knows the identity of the PCs and has no compunction about going after their friends and families.
5) The PCs must by themselves some time and and steal the macguffin from the hunters. Session ends with final showdown with Sariah.
6) Macguffin in hand, the PCs must defend it while they decide whether to side with Victor, Janis, or take a third option. The final showdown may consist of either side or of the macguffin itself, being some sort of sealed evil in a can.