A nice high-level adventure (at least a friend told me, that he liked my idea

) is to have a patron for the PCs, who directs their actions for the cause of good (killing evil, collecting artefacts and strange components). At least that should the PCs think at first. After some adventures the players should become aware, that something is amiss - the bad guys claim to be good, the missions are strangely not so dangerous as they should be, etc.
If the players are good enough, they should be able to discover that their patron is behind of this, using them to further his own dark goal. If they try to stop the patron, they'll find out, that he is too powerful to be killed by them, that he didn't only destroy all proofs against him, but is in the PCs' kingdom a too important figure and thus he can push it away to being a victim of slander.
If they try to break out, they'll soon discover, that the patron lays waste of every town and village, the PCs visit without furthering the patron's goal - and the patron can't be stopped. In the end, the PCs have to free a dead god and discover, that the patron has been the conscious of this god all time along. And as a thank you, the reborn god leaves the PCs alive, only to deal with all the killings and murders of innocent peoples, which are believed to be the actions of the PCs. Then the true adventure begins - survival, cleaning their names and revenge against the god.
This adventure has only three problems, I can see:
1. You have to deal with gods themselves. This means, that you want such a high level of play and that you have to stat out the gods. For this a good resource will be the upcoming Immortals Handbook respectively the PD
F Apotheosis, which will contain the god statting part of the IH.
2. Your last group decided to be the bad guys instead cleaning their names. At least in my adventure, if they are considered to be the bad guys, they are known on the entire world - if they don't have friends, they'll probably be killed from the good guys, so cleaning their names has to be the better option in the long run.
3. It includes railroading. It may be a person of the world, who wants to railroad the PCs, with good reasons, but it can be viewed as a simple DM tool. Probably you'll have to invest some work, that it looks like having gone into a trap - it should create the feeling, that everything is okay at first (so you simply go further), then something seems to be wrong (but you keep going), and then you hear the shutting of door, which is locked up, with no means of return (with the knowledge of coming out of the frying pan into the fire). This stadium should be relatively short, too.
If this idea isn't so ideal for your group, RW, then maybe someone else likes it?