Dark Companion is a volume of two novels by the prolific Andre Norton. The first, Dark Piper, takes place at a time when the planets that comprise the Four Sectors have been beset by a long war. Beltane, a planet of largely rural communities and huge areas of reserve inhabited by strange mutated animals, agrees to give asylum to a ship of refugees. It's a Trojan Horse, though – attack and retaliation follow, and population and aggressors are swiftly devastated by a plague-type illness, leaving only a tiny group of survivors who have been trapped in a cave. The story relates their fight to survive and to discover what has befallen their world.
In the second novel, Dread Companion, Kilda takes on the role of governess to two children, only to discover that the elder has a "invisible friend" who traps them all in a parallel world. While the children quickly assimilate, gaining an understanding of their new environment, Kilda resists, only gradually learning the rules of a world which resembles the legends of Faerie; this both hampers and assists her effort to save the children, one of whom has changed into a faun.
Rather to my surprise, since I often like stories which subvert the conventions of fairytales, I preferred the more conventional scifi world of Dark Piper. This was a very straightforward account of events, although the young survivors must infer the fate which has beset their world, since almost no direct information is available to them. Dread Companion, on the other hand, follows the convention of a fairy tale in that the protagonist must learn the rules as she goes; even the provision of a companion who has been trapped in there for much longer leaves her struggling to avoid her own transformation. Both books are very short, and rather dated (they were published in 1968 and 1970 respectively); they would have benefited from a more leisured pace and, despite my preference, I would judge the second the better in formal terms. Certainly both worth a read – bearing in mind their age, there are some original ideas here. When I was young I was particularly fond of another of Norton's books called Cat's Eye; her writing of the relationship between humans and other animals was unusual and sympathetic for the time, this and her inclusion of legend paving the way for more recent authors such as Liz Williams.