The action takes place in the 19th century on the coast of Cornwall. This area is not inviting to tourists. One day, a young Irish woman named Mary comes to visit her aunt at a small, isolated inn called Jamaica Inn. Her relatives greet her unfriendly. In the county, there is a criminal group of smugglers and murderers that terrifies the local population. Mary meets a guy who works as an undercover agent and infiltrates the criminal community.