The Deadly Virus

"The Deadly Virus" is the fifth series' most anxious hour — a story about four monkeys, a deadly disease and the people who freed them. Animal-rights activists — a young student, Kevin, and the older, harder Jill and Alan — break into a Jersey laboratory, wreck the junction box and release four caged monkeys, one of which is infected with the Marburg virus. Kevin, the student, is bitten as he coaxes the animal out. The virus, as the zoo director Barnard explains with barely controlled horror, can kill people, has a thirty per cent survival rate, and will eventually drive the monkeys into town to scavenge.

Nick McCarty's script, directed by Gerry Mill, is a containment thriller rather than a whodunit, and the series' usual moral shading gets more complicated as it goes. Gaines, the professor running the laboratory, insists animal experimentation is necessary to find a cure for waterborne parasites; Bergerac is not sympathetic. But the activists have not just freed the monkeys — they have loosed a biohazard on the island, and the episode's sympathies narrow as the bodies stack up. Kevin deteriorates in the cottage where the activists are hiding; a tourist is scratched at his picnic; two monkeys are shot by marksmen at a car. By the time the survivors are cornered, the argument has shifted from animal rights to public safety.

The episode's most uncomfortable scene is its climax. Jill, the hard-eyed activist, is surrounded at a farm, a carrier who cannot be touched or approached; Barnard, the zoo man, pleads with her to see the seriousness of what she has done, and Bergerac tells her the cost in plain terms — four monkeys, a dead boy, two tourists spending their holiday in isolation, a family about to be told their son is gone. She wanted to change the world, and she has delivered it to the edge of a plague.

The human cost is brought home through Kim, who does not know Kevin is dying until Crozier says it in front of her. Bergerac, left to comfort her, cannot. It is a bleak, responsible hour — the series warning about zealotry without ever endorsing the laboratory — and a reminder that Bergerac could do thriller and conscience in the same episode. A grimly effective story that stays with you.