Something is afoot in the lonely Cornish village of Merrymaid Bay. Rumours of dead men working in the tin mines have sent a chill through the community, and it's up to the Doctor and Charley to get to the bottom of the mystery.
Can the legends of the Bucca that haunts the mines be true? And just what awesome power do the Doctor's greatest enemies - the Daleks! - threaten to unleash upon the universe?