Episode 4: 'Armageddon', originally transmitted on BBC2, 6 October 1983

Sir Robert Falcon, the new director of London Zoo, returns from an overseas expedition. Simon Carter, the Zoo's secretary, listens to news of the worsening diplomatic situation between Britain and the Middle Eastern state of Bilad al Hawa. His wife, Martha, returns from the United States, where she has left their children for safety.

Carter and Martha visit Falcon at the zoo. Falcon announces his plan for Empire Day, a grand Victorian spectacle. Carter is sceptical about the venture, but the zoo's president, Lord Godmanchester, also a cabinet minister, urges Carter to support the project as a means of raising national morale.

The zoo's keepers make arrangements for war. Sanderson, the curator of insects, prepares butterflies to survive an atomic blast. Price, the curator of birds, plans to smash his aviary's glass to release the birds.

Martha reveals to Simon that she slept with Falcon while she was abroad. Falcon calls Carter to demand that he fetches Beard, the zoo's chief vet, to deal with a sick elephant. Returning to the zoo with Beard, Carter finds a party in progress. Falcon shows Carter further plans for Empire Day; Carter is furious that Falcon is ignoring the threat of war. Godmanchester calls Carter from Snowdonia, where he has retreated to prepare for a post-war devolved government. At home, Martha has moved into the basement in preparation for an attack; Carter tells her that he will know when a war is imminent because the Home Office will order the destruction of dangerous animals.

The next morning, soldiers arrive at the zoo to shoot the animals. Falcon is still oblivious, and his secretary locks him in his office. Carter begins preparing the evacuation. A Home Office official calls Carter to tell him that missiles are on their way in 20 minutes. Carter helps Price release his birds. Falcon escapes and berates Carter with a megaphone from the zoo's clocktower. Price is breaking the aviary's glass roof when a missile destroys the zoo.

Two years later, Carter is awoken from a coma by Emile Englander, the zoo's former curator of reptiles and new director, wearing the uniform of rightwing paramilitary organisation One Europe. Englander tells Carter that he is suffering from brain damage, but that before he succumbed to the coma he behaved heroically in evacuating the zoo. He also informs Carter that One Europe are now in charge of the country.