Guillermo del Toro’s new movie takes place in a lonely boarding school late in the Spanish Civil War, and he fills its closets and corridors with a brooding, somber sense of dread … The school has become an orphanage for the sons of dead Republicans, and in the middle of the courtyard sits an unexploded Fascist bomb: a metaphor waiting to go off. Dr. Cásares and Carmen, the stoical old leftists who run the orphanage, carry some symbolic baggage of their own. Dr. Cásares’s chronic impotence and Carmen’s wooden leg suggest the weakness of the republic, and like that noble, self-divided government, they are unable to defend themselves against the treachery in their midst. The snake in this crumbling garden is Jacinto, a former pupil who is now the caretaker … Since the story is told mostly from the perspective of a young boy, Carlos, who has just arrived at the school, Jacinto’s villainy and its implications do not emerge immediately. Carlos and his classmates are more preoccupied with comic books, marbles and the usual petty rivalries, and also with the ghost, whose eerie whispers trouble their sleep …
El espinazo del diablo is enriched by the contrast between the clammy, greenish light that infuses the orphanage by night and the parched orange glow of the daytime, a tonal contrast mirrored by the story, which melds horror and melodrama. By day we witness the turmoil of the adult world, which is somehow the source of the nightmares that emerge once the sun has gone down.
Eventually these worlds collide, and the film detonates with shocking violence, as all of the subtexts – sexual frustration, class hatred, irrational greed – rise explosively to the surface …
But any easy sentimentality is checked by the gravity of the violence that came before, and by the sobering lessons of history. The measure of Mr del Toro’s intelligence as a filmmaker – and also of his sensitivity to the complexities of his grim story – comes in the last shot, in which a troop of dazed and wounded boys emerges from the orphanage into the desolate sunlight of the Spanish plain. The image lifts the movie beyond horror into heartbreak. Mr del Toro provokes your screams and shudders, but he also earns your tears.

A.O. Scott, “The New York Times”, 21 November 2001