At the lakeside trial, Vázquez de Leca offers only a flat demand for “wonders,” and Luzia realizes she must win through spectacle despite Santángel’s plea that she lose. Donadei, desperate for freedom from Doña Beatriz, complains about the king’s absence. Luzia asks if Donadei’s proposed alliance still stands, and Donadei eagerly agrees, promising they can protect each other against their patrons.

Luzia proposes a miracle tailored to a priest: together they will build an unprecedented cross. She repairs and multiplies the pier’s rotting boards with song-magic, then extends the planks across the lake while Donadei plays his vihuela, drawing fish and birds into a rhythmic display. At the lake’s center, Luzia’s growing structure rises into a towering wooden cross that finally pulls Vázquez to his feet, captivated.

Donadei abruptly hijacks the moment, declaring that the king may want ships, not symbols. His conjured flock tears Luzia’s lumber cross apart and reshapes it into a terrifying galleon with black-feather sails and eel cannons, leaving Luzia dwarfed and seemingly defeated. Luzia realizes Donadei has been using illusion magic and needed her “real” materials to give his creations substance; she recognizes him as the attacker who animated shadows at the puppet show.

Feigning calm, Luzia addresses Donadei by his true name, Fortún, and uses a refrán to transform the jeweled cross he wears: its gems become flying scarabs and writhing ants, and the cross dissolves into skittering spiders. Terrified, Donadei loses control of his words and tune; the birds, eels, and fish vanish, and the galleon collapses into the lake. Donadei lashes out, shoving at Luzia, but she sings boards into a retreating path back to shore, knocking planks away behind her so he cannot follow.

Onshore, the trial site erupts into chaos: the crowd scatters and soldiers surge in as Vázquez shouts from the stage. Santángel grabs Luzia and tells her the true disaster—Antonio Pérez has fled, using the trial as cover, and the king’s men are rounding people up. Unable to ride well, Luzia is helped into Santángel’s saddle, and Santángel mounts behind her as they flee together from the lake and the approaching crackdown.