This plot assumes that player characters are members of an extended family, or clan, and all live in the same castle/villa/manse. My campaign is a RuneQuest campaign set in Carmania, which is a cold and snowy land that was the heart of a splendid ancient empire conquered and kept by warfare, and is now the heart of a growing merchant network.
Strange ship docks at the clan village, word is sent to the clan to pick up Farwalker, the chief's half-brother and wandering-merchant/ capitalist-oppressor-pig who has been gone for many years. He is sick, very cold, and is clutching something in his hands. His hands cannot be pried apart without breaking his fingers, something the chief (in my campaign his nickname was Stoneface, but the PCs called him "chief") would be very upset about.
Chief installs his brother in a sickroom, and appoints a PC to watch him, alternating with other family members. A rivalry would be a good thing to encourage here, because it makes the rest of the plot possible.
Word comes that someone has been killed in the village. PCs are sent to investigate. Discover several brutal murders. Chase the murderer around, path leads to the clan house/castle/villa/manse.
While the PCs are out of the room, the rival searches through uncle Farwalker's clothes and finds something, half of an ivory idol, and removes it to his rooms. Then he comes back, pretending nothing has happened. In the meantime, the murderer has snuck into the sickroom, put out the lights, and is killing uncle Farwalker as the rival walks in and lights a candle to see what's going on. The murderer is a yeti or some other huge, hairy, tough humanoid (in my campaign it is a snow troll from the glaciers) which was looking for an idol that Farwalker took.
The PCs come in about the same time that the rival is being ripped up by the murderer and join the battle. What happens after this is up to you, but the PCs will probably discover the half idol, should interrogate the rival, may want to find where the idol came from, may want to return it, and may have to deal with more attempts to recover the idol. And... the idol might be cursed, or blessed, or an ingredient in a world-shattering magical ritual.