The children Colin and Susan, after their involvement with the world of myth and magic, are several months on from the events of Brisingamen and are troubled and a little bit angry that the magical world they saw so briefly has turned its back on them, as if they are no longer needed now they have played their part and surrendered the weirdstone to its rightful owner.
To ease the surrender of the Weirdstone in The Weirdstone of Brisingamen, Susan was given a magical bracelet by Angharad Goldenhand. Her assumption of this bracelet has launched Susan unwittingly on a destiny connected with the cycles of the moon, and hence the older wilder powers of the world (perceived in a rather chauvanistic way as being unbiddable and female). The Moon of Gomrath begins when the elves (lios-alfar) borrow the bracelet, with her consent, to see if its power can be directed by them to battle an unknown evil power in their own lands in Sinadon. However while unprotected by the bracelet, Susan is possessed by the Brollachan, an ancient evil released after an old pit is broken open during building work. The wizard Cadellin, guardian of the sleeping knights in The Weirdstone of Brisingamen, cannot restore Susan after the Brollachan has been driven out of her body; instead perceiving that her spirit has been driven to voyage in other spiritual dimensions analagous to Heaven and Hell, unreachable with ordinary means. It is Colin's true-hearted heroic love and need for his sister which provides the answer; as he too responds to the older powers of the world. He therefore comes to seek the Mothan, a mythical plant which grows on the Old Straight Track, by moonlight. This is a motif inspired by the book of the same name, which is part of the Old Magic, in contrast to Cadellin's High Magic. Susan is dramatically restored to her own body.
However, her exposure to other levels of existence has sensitised her to the powers with which she and her brother have been coming to associate and the story takes a new dramatic turn. On walking home across the Edge on dusk, they are inspired to build a fire to keep warm, Susan almost manically so. This fire includes rowan and pine which unintendedly act as a wendfire, which on this night of the year has the power to call ancient spirits from their mounds. Colin and Susan release the Wild Hunt, which return several times during the course of the novel.
While they are trying to undo what they have done, the Morrigan, acting through an evil Dwarf working for the Dark Side, captures Colin and imprisons him in Errwood Hall, a ruin in this plane of existance which her magic restores into its full glory. However, when not bathed in moonlight, the interior of the Hall exists only in a lightless magic realm. This sets up the denouement, a pitched battle between the forces of the Morrigan (goblin-like bodachs and wildcat palugs) and Susan's allies (the lios-alfar, the dwarf Uthecar, and man Albanac), both willing and unwilling. Although Colin is rescued, Albanac is killed. When the elves withdraw their support as a lost cause, the Morrigan finally releases the Brollachan, focusing it on Susan to destroy her growing potential as a force for good. Colin blows a horn, his gift from Angharad Goldenhand, which saves the day and the Old Magic is set free forever. Susan glimpses the Daughters of the Moon riding into the stars with the soul of Albanac and yearns to ride with them, but is pulled back into the human world (for now) by the intervention of Angharad, who promises her that one day the time will come when she may ride with the sisters.
Continued in Boneland (2013).
Light wendfire on the mound on the Moon of Gomrath, and these tropes may be freed to walk the Earth:
- All Witches Have Cats: The Morrigan takes this to extremes. It is clear that the palugs, the pack of killer wildcats, love and adore her and want nothing more than to be by her side.
- Firearms Are Cowardly: Facing an attack by palugs and bodachs, Uthecar disagrees strongly with Colin's suggestion that they'd be better off with guns — he thinks killing at a distance means you don't apppreciate the cost of each death, and isn't particularly happy even with the bows and arrows the elves use.
- Garden of Evil: the rampant, fast-growing rhododendron infestation at Errwood Hall, an imported foreign flower that has few predators, is steadily strangling all plant life other than itself, and among which nothing else can grow. Colin and Susan both get entangled in its spiny, thorny, runners.
- Gratuitous Latin: the dark spells fired and chanted by the Morrigan are in Latin. Word Of God is that these are partial extracts from a real mediaeval grimoire (see the author's appendix to the book).
- Meaningful Name:
- Also a Bilingual Bonus and a case, perhaps, of Readers Are Geniuses. In The Moon of Gomrath, the dwarf Uthecar reflects on the name "Colin" and says it is that of a great hero. He even calls Colin the "Grey Dog". Colin, of course, is a modern form of the Irish hero's name Cu Chulain, the Hound of Ulster, the original Grey Dog.
- More tangentially, the name Susan ultimately derives from a flower-term variably associated with the lily (death and rebirth) or the lotus (spiritual awakening), and is associated with a Middle Eastern deity of protection and guardianship. During this book Susan symbolically "dies" and sees the afterlife; she is spiritually awakened by her exposure to other realms; and she fights in guardianship of things she loves and protects.
- No Communities Were Harmed:
- Alderley Edge, Macclesfield, Mobberly, Lindow and Wilmslow are all real places in Cheshire. Most of the places mentioned in the book along the Edge; The Wizard's Well, Goldenstone, the Beacon and so on are also real. Although Garner is describing the Alderley Edge of fifty years ago, when it really was an isolated farming village in Cheshire a long way away from the nearest city, a long time before it became popular with professional footballers and other people with lots of money and no taste. South Manchester has also encroached vastly in the fifty years since this book was written.
- The news report from the Stockport Advertiser about the weird goings-on at the pub in Alderley note is a genuine news report from what was then a genuine local newspaper.
- Errwood Hall, the scene of the final battle, genuinely exists in the Vale of Goyt, and these days is a scenic ruin managed as a historic site and beauty spot. It is renowned for its rhododendrons.
- Old Magic: The Wizard Cadellin is a Guardian of the High Magic and speaks, in a somewhat sniffy and condescending way, about the wild untamed Old Magic being a thing for women and witches, and that it's a damn good thing this was tamed and shut off from the world. He is not best pleased that Susan gave it a doorway to return when she lit wendfire on Gomrath Eve.
- Our Elves Are Different: The lios-alfar, who are drawn from Welsh mythology and whose society is organised along pre-conquest Welsh lines.
- Our Goblins Are Different:
- The Svart-Alfar, although the name actually means 'dark elves' (but the Norse version from whom they take their name are more like goblins).
- In this book, the goblin role is taken by bodachs, creatures from the far north (Scotland) who are likened to humanoid lizards. Bodachs organise as warbands, wear minimal armour, and fight with spears. They are supported by palugs, supersized wildcats.
- Panthera Awesome: The palugs, which are giant wildcats.
- Place of Power: Practically every tor, summit and geological feature in the Cheshire Peaks in and around Alderley Edge. Linked with a network of Ley Lines, apparently.
- Possession Burnout: an ancient Celtic demonic entity, the Brollochan, is released from its prison cell by human interference. The Brollochan is an entity that lives vicariously through the senses of people and animals it serially possesses - but no host can contain it for long without burning from the inside and crumbling to death.
- Power at a Price: When Angharad Goldenhand gives Susan the horn Anghalac, she warns that it is only to be used when all else is lost, because once it is sounded you will never know peace again for the rest of your life. At the end, when it is used, this is stated to be its effect on Colin. This is a theme to be developed in the concluding book of the trilogy, Boneland.
- Shown Their Work: There is a long postscript/appendix to the novel, in which Garner discusses folklore and mythology and explains the roots of many of the characters and situations in the age-old stories. He is keen to show that none of it is made up, even explaining that the Latin spells are taken from a medieval grimoire but are only partially reproduced, for safety's sake.
- Stellification: The fallen hero Albanac is last seen in the sky. The stars rearrange themselves to show him outlined as a very clear constellation, riding off in the company of the Valkyrie-like Sisters of the Moon.
- The Wild Hunt: Colin and Susan, infused by the Old Wild Magic, spontaneously decide to light a bonfire on a bleak hilltop in the Peak District. note Unconsciously they are fulfilling an age-old magical ritual that summons the Wild Hunt. Who duly turn up demanding to know who has called them into the world. Fortunately Susan wears a bracelet advertising she is now an avatar for one third of The Hecate Sisters, and they kneel in homage to her.