3x1 - Fire and Brimstone

June 5, 1972

John Ridge apparently suffers a breakdown from the pressure, and decides that, due to the excessive threat of pollution on the environment, drastic steps should be taken. He steals some phials of the deadly virus anthrax and holds the government to ransom: unless his anti-pollution terms are met, he will destroy humanity by releasing the virus in a number of major cities. A race against time begins. Can Ridge be tracked down before it is too late?

3x2 - High Mountain

June 12, 1972

An inquiry into Doomwatch is begun following the events surrounding Ridge's breakdown. Meanwhile, Quist is summoned to a large country estate in Scotland, where he finds himself offered a new position with both power and wealth in the private sector, but only if he will curtail his investigations into a new drug called disocyanate. Back in London, the Minister decides that it is time to place his own man within Doomwatch, and so despatches Commander Neil Stafford to join the team.

3x3 - Say Knife Fat Man

June 19, 1972

Many years ago, Quist worked on the infamous Manhattan Project, which was instrumental in the designing of the atomic bomb codenamed Fat Man, used to obliterate the seaside port of Nagasaki in World War II. This involvement has continued to weigh heavily on Quist's conscience ever since. Hearing the phrase "Say knife," he recognises a potential threat - one that is tied into a break in at a plutonium base. A group of young student activists has stolen several radioactive fuel rods, and are planning to construct their very own atomic device.

3x4 - Waiting for a Knighthood

June 26, 1972

A vicar collapses during a sermon, and there are seemingly unrelated events, one involving John Ridge. The answers are out there, but are obscured by big business and profit margins.

3x5 - Without the Bomb

July 3, 1972

A revolutionary new lipstick goes on sale, containing pheromones designed to act as an aphrodisiac in order to make the wearer more attractive and desirable to men. This prompts Quist and Bradley to begin an investigation into the effects that pheromones have on people, and how they can alter the illusion of free will.

3x6 - Hair Trigger

July 10, 1972

A radical new procedure has been developed for treating violent criminals. The results are extremely positive, but Anne Tarrant is not convinced of its ethics.

3x7 - Deadly Dangerous Tomorrow

July 17, 1972

Ridge continues his ecological crusade by warning against the dangerous side effects of the chemical insecticide known as D.D.T. upon the world's developing countries. He stages a publicity stunt by flying in an Indian family and setting them up in a tent in the middle of London's St. James Park. But the prank backfires when it is discovered that one of them is suffering from malaria.

3x8 - Enquiry

July 24, 1972

Doomwatch is alerted to a laboratory where a new toxic gas is being developed for military use, available in a 'handy' aerosol can for easy application during conflict. But Quist and Anne's enquiry soon leads them to doubt that the scientists' safety measures concerning the storage of the gas may not be as secure as they think.

3x9 - Flood

July 31, 1972

Quist is concerned by the fact that, approximately every one hundred years, certain extreme weather conditions arise which lead to an increase in the water level of the Thames - and just one inch higher would result in the whole of London flooding. Even more disturbing is the fact that this increase is imminent.

3x10 - Cause of Death

August 7, 1972

When John Ridge's father, Wilfred, becomes seriously ill, he decides to devote all his time to looking after him. Wilfred is then taken to hospital and put into the care of Doctor Cordell, but shortly afterwards he dies. Ridge is suspicious, and his investigations uncover a disturbing fact: Doctor Cordell is an advocate of euthanasia.

3x11 - The Killer Dolphins

August 14, 1972

Dolphins have long been established as highly-intelligent creatures, and the United States Navy has now begun using them in their new program. They are training the dolphins to act as underwater saboteurs, able to attach magnetic explosive devices to the undersides of enemy ships. Quist investigates the matter, and discovers that these apparently docile creatures are capable of becoming deadly killers - something that he experiences firsthand.

3x12 - Sex and Violence

Doomwatch's Anne Tarrant and Spencer Quist are placed on a government committee investigating whether the UK's censorship laws should be revised. The committee's work brings them into contact with both anti-pornography pressure groups and a man who hopes to one day be a dictator.