Trujillo is the dictator of the Dominican Republic. He is more than a political figure; "El Jefe" is a symbol of the power of the Dominican state and of the hope for a better future. Trujillo nurtures a "cult of personality" around his identity; ordinary citizens proudly display photos of him as a symbol of progress and hope.
The "secret" of Trujillo is that he is not the benevolent man people think he is. Minerva learns this from Sinita at their convent school. Sinita tells her that the secret of Trujillo is "that we can all be killed," and she explains how Trujillo has murdered all the men in her family. At first, Minerva cannot believe it: "It was as if I had just heard Jesus had slapped a baby." But then, she begins to experience a "china crack of doubt" as Sinita continues her story, which includes an account of the way Trujillo climbed into power by betrayal, double-dealing, and the outright murder of those who opposed him.
Sinita says that her three uncles planned to "do something" to Trujillo but were found out and "shot on the spot." Then, two other uncles were killed for opposing the government. Then, her father was killed. Then, finally, her brother, José Luis, was murdered by an agent of Trujillo, a lottery ticket vendor they knew and trusted.
Trujillo's secret is that anyone can be killed, at any time; worse than that, these killings are not simply retribution, but acts of personal vengeance.