OK, so it could be considered weird to have a protagonist who isn't even born until midway through the novel. That's why we're qualifying this assertion with a "maybe." But, since it turns out that practically the whole story is told from Alba's perspective (minus the little interludes from Esteban Trueba), we think we've got a pretty good case here. Plus, one could argue that Alba and Clara are so strongly bonded that they can be seen as two halves of the same whole – Alba even confuses her own life with her grandmother's. She writes, in the Epilogue: "At times I feel as if I had lived all this before and that I have already written these very words, but I know it was not I: it was another woman" (Epilogue.45). Go team protagonist!
So while Clara is central to the first two-thirds of the novel, Alba takes center stage for the most climactic parts. Our younger protagonist is active as part of the resistance to military regime, she's kidnapped and tortured in a secret military prison, and her release from prison brings about the novel's denouement, or resolution.
On the other hand, maybe you're not buying our brilliant argument about Clara and Alba making up a fierce feminine duo of protagonists. Maybe you'd feel more comfortable with a traditional, solitary kind of protagonist. One who lives through the entire book, perhaps? OK, fine. But your options are limited here – Esteban Trueba's the only character to make it from Chapter 1 straight through the Epilogue. Those arguing for Esteban to be recognized as the protagonist have a few good points in their favor – a lot of the narrative is told from his perspective, after all, and he does precipitate a lot of the action of the novel. Take a look at our analysis of plot structure, and you'll see that he fits neatly into the role of hero using Booker's "Rebirth" paradigm.