In a small inn (the more remote the better), a man turns up dead. There are no wounds on his body what-so-ever, and he aboslutely reeks of garlic.
The man died of a curse that forced him to eat a clove of garlic a day or suffer the penalty. This gets really interesting if the body somehow appears on top of a someone the villagers are suspcious of.
Another real world thing. White tea. Can only be picked two days a year, the two days before the flowers blossom. Could be a similiar plant that...is the deadliest poison known, cure known diseases or psychosis, or a potent herb that just tastes awesome.