A trilogy of games in the style of Flashback (or perhaps something like Shadow Complex) in which you play a detective in Victorian times who is investigating the disappearances of some people in a remote area. Halfway through the game you discover that it's a den of werewolves "recruiting" new members. There is a fight, and you get bitten. The rest of the game is spent not only trying to track down the pack leader, but also a cure. The last portion of the game is timed and if you turn before completing the game then you lose, game over. You eventually do find a cure.
The "cure" is an herbal remedy that you have to take on a regular basis or else you will turn. The werewolf's curse is still active though, which grants long life (almost immortality, but not quite... you just age VERY slowly) and vitality, but also torment and loneliness and blah blah blah stereotypical character crap.
The next game takes place in modern times, and the final game some time in the future (probably pretty close to Flashback-era flying car type future, actually). Both deal with yet more supernatural shenanigans, creepy creatures, magic, etc. I have the story line pretty much laid out in my head, and have for some time, but I have yet to seriously consider any details or plans to make such a thing because man... that's a lot of friggin work for one person.
And yeah, I know, it's all very derivative but I like those themes so sue me.