Jamaica Inn is headquarters to a gang of smugglers, led by the innkeeper Joss. The smugglers conceal coastal beacons in order to cause ships to run aground. Then they loot the wrecks and kill the surviving sailors.
Mary, the orphaned niece of Joss's wife Patience comes to live at the inn, and saves the life of Traherne a gang member lynched by his fellow smugglers for embezzling. Traherne is actually an inside man, trying to bring down Joss' gang. They flee the inn and seek the protection of Sir Humphrey Pengallon, the local magistrate, little knowing that that he actually protects Joss' gang, as he needs the loot in order to maintain his lavish lifestyle.
Traherne and Mary must race against time to stop a ship from being wrecked, and an unlikely love affair blossoms.