It is initially set in
Japan following the end of
World War II and follows the story of Nicholas Linnear, a man raised by
Anglo-Chinese parents. As a youth, Linnear is introduced to the world of
aikido,
kenjutsu, and
iai-jutsu at a local
dojo of the
Itto Ryu, also attended by his cruel and violent older cousin Saigō. Linnear is a natural and soon becomes adept, much to the annoyance of Saigō. During a training exercise Nicholas and Saigō duel, and Nicholas defeats him. Saigō is enraged and leaves, swearing revenge. When they next meet, Saigō is a considerably more skilled martial artist than Linnear and defeats him quickly. It's revealed that Saigō has joined a
Kuji-kiri ryu in order to learn black
ninjutsu and has become a
ninja. Linnear himself soon becomes introduced to
Aka i ninjutsu, or the red, ostensibly "good" side of ninjutsu, through the
Tenshin Shoden Katori Shinto Ryu. The
ninjas are introduced not as magical or mythical beings, but rather as supreme martial artists who have reached the highest level and seek to progress further. It is suggested that, by becoming
ninja, they strive to advance to an even higher plane, gaining skills such as
haragei, or sensing the surrounding world in a different manner. However, this process is accompanied by a significant cost. Many years later, Linnear has moved to
America and leads a peaceful academic existence. After quitting his job in advertising, he meets a beautiful, if disturbed, woman called Justine, with whom he falls in love. This peace is shattered when a prominent local businessman is murdered in an extremely unusual manner (by a poisoned
ninja shuriken). The local police are baffled and consult Nicholas, as he is known to be an authority on oriental studies. Linnear quickly realises that a
ninja is the murderer and the next target is his new girlfriend's father, Raphael Tomkin, for whom he starts working as a bodyguard, although not without persuasion. Linnear also befriends Lew Croaker, a local detective. Linnear's investigations reveal Saigō is the
ninja, and this puts him on a deadly collision course with his older cousin. ==Unmade film adaptation==