The Fires of Heaven introduces the almost insurmountable obstacle that the male and female heroes cannot work together.
In the series as a whole, the middle act is where a variety of obstacles are encountered. There are always external threats like villains and monsters which can be vanquished. In the previous book The Shadow Rising the heroes overcame a lack of resources to accomplish their goals, ending with Rand acquiring a teacher and an army. More insidious, and far more difficult to overcome is an obstacle that comes from within, where the Heroes very character traits work against them.
To establish the danger, there have been frequent mentions of how men and women working together in the Age of Legends performed tasks that neither could have done on their own. Since the series follows the heroines as much as the heroes, readers reasonably expect the ultimate victory over the villains to be the result of cooperation between men and women.
The Fires of Heaven effectively drives a wedge between the sexes, firming their misgivings into mistrust. Whereas differences between the sexes may have been remarked upon in a candid or humourous manner in previous books, now the criticisms are biting, intended to show chasms between them that are far greater than those between any cultures. Tension between the sexes reaches its climax when Lanfear’s jealousy exposes Rand’s unyielding patronizing sexism.
Rand can’t let women be what they want to be. Rand can’t understand the motivations of women. Rand can’t trust the powerful women in the White Tower or amongst the Wise Ones. Following Lanfear’s attack, Rand decides the only way to free himself of the burdens that he feels women place on him is to drive them away. He does this even though Nynaeve just showed him that separately they will be beaten, but together they defeated his enemies.
Several other characters also exemplify this rift. Elayne takes a female warder when they have always been male. Siuan proves that women can’t be trusted to keep their word to men in authority. Gareth Bryne puts a metaphorical noose around his neck because he pursued a woman. Leane actively sets out to play with men’s expectations. Poor communication between Nynaeve and various men leads to riots in Samara. Mat’s lover was hiding a dark secret. Lews Therin makes his first appearance and reminds Rand that he killed the woman he loved. Perrin is not in this book because the cooperative behaviour of the Two Rivers folk does not fit the theme of poor relations between the sexes.
The other big shift in the series is the deliberate move to mystify events, motivations, and objects. Secrets have always been present in the story, but in The Fires of Heaven the tone is different. In the previous book, readers were introduced to a host of new fantastic places and enemies. In this book, the revelations are more mundane, less magical, and are given up grudgingly. For example, Rand wonders about Aviendha’s necklace several times, even though readers know it is a friendship gift from Egwene. Asmodean’s existence is kept from everyone, and what he reveals mostly happens off-page, with hardly any emotional importance. Lews Therin’s brief appearances offered better insight than Asmodean’s. Asmodean’s murder would set off a decade of internet speculation, but the author could just as easily have named the killer on the spot since it was a detail of little plot significance. It shows a change in the tenor of the series, where information is now compartmentalized, and the author has a stronger desire to keep the reader wondering and frustrated by the lack of answers, for plotlines both big and small, relevant to the plot or not, perhaps to mirror the characters’ own emotions.
Subtly or blatantly, every detail and event in the story can be made to fit the theme.