The Adventure Seed
A rich and influential patron and friend of the PCs has a dark secret: When he was younger and poor, he was shipwrecked on an island with an active cargo cult among the native population (which occasionally found cargo from wrecked ships which washed up on their shores, as their island was fairly close to a difficult section of a major shipping lane). He was able to take over the cult, and finally convinced them to send him away on a large raft with all their gold and gems “as an offering to the gods”. He returned to civilization, and used his new-found wealth to build a major business empire.
Some time later, the islanders made contact with traders from a major civilization, and learned that they have been duped. And now they are plotting their revenge. But they don’t want to merely kill their former cult leader - they want to make him suffer first. As a first step, they have slipped highly illegal drugs into his luggage when he visited another country, and now he has been rescued by the local authorities.
Their friend now contacts the PCs to get him out, claiming that he is innocent of this crime - and he is. But even if they free him, the revenge schemes of the islanders won’t stop - and eventually they will learn how he gained this wealth. Do they continue to help their friend against the attacks, or will they turn away from him in disgust?