Santiago is a male figure who appears in the narrator's consciousness after her failed attempt at suicide at the age of fourteen.
He arrives to supplant Mina, a childlike creature of the mind who has shepherded the narrator through life from birth onwards but whose lack of worldly wisdom has created problem after problem for her host as she blunders through school, never quite understanding why she never gets things right.
The vulnerable innocence of life with Mina grows more distressing than ever with the onset of sexuality.
With Santiago's arrival Mina is driven away, and as an adult the narrator achieves unprecedented successes, as she walks Santiago's way, but never feels truly herself.
Her adventures in Madrid and London gradually reveal the downside of Santiago and the paranoia that underlies his worldly wisdom.
Returning to Mexico, she manages ten years of marriage before Santiago turns against her husband...