Robert Hardy and Deborah Stan ford return tonight as the Stewarts, installed in the Caribbean. Alec is involved in an explosive situation. Mogul's drilling rig on the island has been sabotaged. Stead sends Alec's old rival Thornton out to investigate.

Albert Lefioch, veteran of Verdun, stages a one-man strike and brings the whole of France's canal system to a halt. Since the barge traffic includes a vital consignment of secret oil for Concorde, Mogul is deeply concerned.
Meanwhile, in England, another old man succeeds in stopping the Mogul refinery which produces the oil.