The Clean Air Act (short story)

 was the fourth short story in The Target Storybook.

Publisher's summary
to be added

Plot
Returning from a scientific conference at Tarminster University, the Doctor and Jo discover a number of people lying in the gardens of a housing estate in Oak Green: all have inexplicably choked to death, except for a young girl named Sally Hesketh, who sits among them unharmed. The Doctor and UNIT are unable to determine the cause of death, although Sally’s parents appear to know more than they let on. Life in the village resumes – until a second incident occurs a few days later, and more of the Heskeths’ neighbours suffocate. Realising that the air around the Heskeths’ house has been drained away, the Doctor confronts Sally’s parents; in response Mrs Heskith turns into a fibrous, vegetable creature, which attacks the Doctor and joins its mind with his. Through their connection, the Doctor learns how Mrs Heskith ate an alien plant that her husband found in Papua New Guinea; the alien parasite has been draining off Earth’s air through a space tunnel, using it to replenish its own dying world. Struggling against the creature, the Doctor is able to cut it off at the roots using the folding metal frame of a sun-lounger. With the alien threat destroyed, UNIT closes down the village, attributing the incident to toxic paint cans buried during the war.

Characters

 * Third Doctor
 * Jo Grant
 * Alistair Gordon Lethbridge-Stewart
 * Mike Yates
 * John Benton
 * Tom Hesketh
 * Jenny Hesketh
 * Sally Hesketh
 * Anoushka Mastersson

Worldbuilding
to be added

Continuity

 * Extracts from Sir Charles Grover's book Last Chance for Man are seen throughout the story and it ends with the Doctor writing to Sir Charles politely declining to write the foreword to the book. (TV: Invasion of the Dinosaurs)
 * Yates and Benton at one point discuss the possibility of Anoushka being, Yates waves it away saying "He's good... But he's not that good." (TV: Terror of the Autons et al)
 * Jo is becoming more environmentally aware and wants to go with Anoushka to a demonstration at Stonehenge. (TV: The Green Death)
 * Oak Green is not far from Tarminster. The Doctor uses readings from the Beacon Hill Research Establishment to deduce the nature of the sudden loss of air around Oak Green. (TV: Terror of the Autons)