To ease the surrender of the Weirdstone in "The Weirdstone of Brisingamen", Susan was given a magical bracelet by Angharad Goldenhand. It is the donning of this bracelet which has launched Susan unwittingly on a destiny connected with the cycles of the moon and hence the older wilder powers of the world. "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 another spiritual dimension, unreachable with ordinary means. It is Colin's true-hearted heroic love and need for his sister which provides the answer; as he responds to the older powers of the world. He therefore comes to seek the Mothan at moonrise. The Mothan is a mythical plant which grows on the Old Straight Track. This is a motif inspired by the book named "The Old Straight Track". It is part of the Old Magic, in contrast to Cadellin's High Magic. Susan is dramatically restored to her own body.