Stead, Thornton and Izard are on trial tonight. State secrets have been leaked to a foreign power - and the Ministry of Defence investigator says it must be from one of these three men.

In this final episode, the action all takes place in Mogul House as Commander Fayne (Patrick Allen ) conducts his interrogation.

Industry, pollution, overcrowding - Stead is feeling the pressures of them all when he goes to Nova Scotia. Here, he finds the perfect site for Mogul's ne-v refinery.
But is it perfect? In the peace of a small country hotel, Stead finds time to think.

Giant submarine tankers have been a dream in the oil industry for years. Now, they are not only possible but necessary-to ship oil out of Alaska under the ice.

Mogul's experiments have gone well. Now Stead, Thornton, and Izard visit their submarine - not in Alaska but in the Caribbean. Even there, though, things can go dangerously wrong - as Stead finds on his first underwater dive.

Negotiating for a refinery contract in Africa is never simple. But when Chinese, American, Rhodesian and African interests are all involved, the task becomes almost impossible.

It is said that there are more spies per square mile in Kinsaka .than anywhere in the world - and most of them seem to be after the men from Mogul.

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.

Tribal quarrels, witch-doctors, political double-dealing, a drunken hotel-keeper and a mysterious blow-back on a decrepit drilling rig -all hundreds of miles from nowhere in the African bush ...

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.

Haiti is notorious for voodoo and its secret police, the dreaded Tonton Macoute. Stead becomes involved in a desperate and dangerous battle for control of Mogul's local company.
All the location film for this story was shot in the Caribbean, with Geoffrey Keen , Ray Barrett , and Philip Latham plus the other star of the show-the Dangerous Green Impala itself.
The Tonton Macoute are President ' Papa Doc ' Duvalier's personal and not very secret secret police force who use a combination of voodoo magic and good old-fashioned brutality to keep Haiti in ' Papa Doc 's ' good books.

How do you tempt a man who has everything? Mogul's future in South America depends on the answer, which occupies Stead, Thornton and Izard.
Their attempts to pin down a multi-millionaire to talk business take them to a health farm, the Cannes Film Festival, a Continental casino, and a Scottish cattle sale.

In the desert, water can be just as valuable as oil - and as explosive, as Peter Thornton finds out to his cost.

When management efficiency experts arrive, rumours of redundancy swamp Mogul head office.

What is it like to be captured by dangerous mercenaries in an African civil war? Willy Izard finds out the hard way when he replaces Thornton on a trip to Ebon.
Mogul's frantic efforts to free him centre on Jane Webb, Stead's former secretary (Philippa Gail), and her husband - a mercenary officer played by John Barcroft, best known for his performance as George Forsyte in "The Forsyte Saga".

What is the price of a bride? When the government of the African State of Manzaya decide to throw out Mogul's manager, three men are faced with this question: Ralph Grant , the manager with a South African wife; Jack Robbins , who lives upcountry with an African girl; and Peter Thornton himself.

Mogul's drilling operation in Alaska is disrupted by one Eskimo with a high-powered rifle. But is it just one man? Life on the North Slope is tough. But during the ballyhoo of an oil-men's convention in Fairbanks, Stead and Thornton discover that there are human problems in Alaska too.

A world-famous leprosy hospital lies in the path of Mogul's exploration teams in East Africa. The ageing Dr Hoffmann who runs it is idolised by millions, including Willy Izard - who, with Thornton's help, has to cope with the problems involved.

Stead's visit to a Mogul refinery in Africa causes problems for Peter Thornton. The simple job of organising a ceremonial event becomes highly dangerous when a sacked engineer threatens to blow up the refinery.
Exciting film sequences shot in Africa range from a modern refinery to the ruins of a lost city in the jungle, and a desperate drive across hundreds of miles of African bush.

Stead's back in his haven, all's right with the world. But his quiet trip to the Caribbean on a Mogul supertanker produces unexpected developments.