This is the first part of a series of blog posts about taking inspiration from real life events to create evocative adventures.
The River of Doubt
A great leader has gone into retirement, (having stepped down from his throne, passed in on to his son, or perhaps he is in exile after a coup). Looking for a new challenge he has gone on an expedition of discovery to find chart a treacherous river or in a dangerous and unexplored wilderness. However unlike the expedition that inspired it, things got worse. The retired leader and the other members of his crew have gone missing, and a dead body is found. The government hires the PCs or perhaps offers a bounty for the return of their revered leader (even if its just his body, for a state funeral). This is an excellent adventure to introduce a new complex race native to the area previously known only in rumor. And you can spend a good deal of time searching for clues, or following false leads.
Twists: The retired leader has become injured by some affliction that cannot be cured until he is removed from the wilderness, but the curse makes his quick removal difficult, The new leader or an old enemy does not want the old one to return and sends an assassination team instead of a rescue team, the retired leader won't leave without his youngest child who accompanied him but is held elsewhere. The retired leader does return and attempts to retake his position leading to civil war, a golden age, or perhaps having lost his son to the assassins he becomes a tyrant. The PCs fail to save the retired leader causing everyone who loved him to blame the PCs for his death (and perhaps they are responsible as one of their members killed him for the government, to avert civil war, or prevent him from becoming a tyrant).