The local merchants are growing restless. Their shipments are being intercepted and utterly annihilated. The shipments (and the bodies of all escorting them) have been taken, leaving all but the unusable wrecks of carriages and wagons in their wake. The party is hired to investigate the most recent of these attacks, to solve who or what is behind all of this.
-Who the attacker is
-What is happening to the loot and bodies
-If any supernatural events are in play (NPC adversaries are great)
-Economical turmoil in the local area; who is or isn't affected by this blow to business? Are merchants going to pay the party to smuggle their men onto a rival's ship as stowaways to get word out to their customers?