Tom and Nell dock their boat in Montliskeard Bay, focusing their conservationist efforts on the lost waste drum. Martha abuses Luke's clairvoyant visions of the past, and Nell sees him escaping his abuse in the mansion on the bay cliffs.

Tom seeks out Fran Tuett, a local news reporter. Nell speaks to Luke on the boat; learning of what he saw in his visions, she goes diving to find the cave. Martha pressures Runceford to stop potential interference, and Nell is attacked.

Nell escapes the diver's attempt on her life, seen in a vision by Luke. Martha tracks down the last of the Montliskeard descendants, keepers of the stones. Tom's boat is suddenly held under ship arrest over supposed drug trafficking.

The gem holders arrive in Montliskeard Bay for Martha, however one of them, Rob Appleton, goes rogue and agrees to try and help Luke out. Tom and Nell face danger again as they meet a wolf in 'green' clothing.

Tom and Nell find their work smashed and Rob knocked unconscious on the boat. In spite of the previous attack, Nell decides to go diving again so that Luke can be reassured. Meanwhile, up at Montliskeard Place, Barnes falls foul of Martha.

Martha is closer than ever to achieving her evil goal. Rob and Fran attempt to stop her, and are held prisoner. Nell launches a desperate last-ditch bid to rescue Luke from the cave, preventing Martha's ritual from unleashing destruction.