The heroes find a small crypt somewhere and being brave adventurers they want to check it for evil forces (=graverobbing). Or for any other reason.
The PCs are stuck in a town with a strict peace policy, the tiniest scuffle can land you years in prison. The town also happens to be a tourist haven, so inn-prices have skyrocketed. The only way the PCs can rest is if they splurge on a room, with their enemy.