Heartsease

<ul><li> 'At a future time in England when anyone knowledgeable about machines is severely punished as a witch, four children dare to aid in the escape of a "witch" left for dead.' --summary, WorldCat library record {{OCLC|973655029}} <li> "The story--a kind of reverse science-fiction--tells how two children rescue a near-dead witch (an American observer with a two-way radio) ..." --brief review by {{a|Naomi Lewis}}, <i>The Observer</i> 1969-08-03 p. 25 </ul>

Concerning the 1st Puffin edition in 1972, perhaps in a new printing or state: A brief review of book 3 in "Briefings" edited by Helen Dawson, The Observer 1972-08-27 p. 22, closes "Don't miss the other two [...] (Puffin 20p each)."