What do you call fear? It’s a question Wagner’s hero asks as he runs a gauntlet of perils with unshakable casualness in Siegfried. About to fight a savage dragon in the depths of a forsaken wood, Siegfried calls out “Here, then, is where I learn fear?” But it’s not fear that’s the real question in the end – it’s what to call love.

The third part of Houston Grand Opera’s Ring Cycle, which concludes a year from now, Siegfried is a co-production of Palau de des Arts Reina Sofia, Valencia, and Maggio Musicale Fiorentino. In line with the heavy recollections of the first act, the indefatigable Barcelona-based theater company La Fura Dels Baus brings back many familiar production favorites here from Das Rheingold and Die Walküre.

The production is a disconcerting combination of cold metallic future and Neanderthal aesthetics – a startling pairing of humanity’s beginning and its end. Siegfried, dressed in thigh-length leather and pelts, his long blond hair tied back in dreadlocks, forges Nothung, his matchless sword, against a backdrop of grinding machinery and minions in white hazmat suits. A laboratory replaces Mime’s hearth, lowered from cables with beacons of white frothy chemicals and gassy water against a backdrop of shifting screens with video images by Franc Aleu.

Vocally, it’s a demanding work especially for the tenor in the title role, and Jay Hunter Morris showed its wear. Morris caught the simpleton brawn of Siegfried well, but his voice began with a husky edge that opened up beautifully at the end of Act I only to then wane thinly. I wondered if he might be pacing his voice for the final scene with Brünnhilde, where, after four-plus hours Wagner asks a singer to belt out an opulent and tender duet, but nothing changed when the scene finally arrived.

But Siegfried welcomes back many astounding voices from operas past, a happy result of Wagner’s four-part design. Bass-baritone Iain Paterson, as the Wanderer, again performed with heartfelt solemnity and vigor. As the scheming Alberich, Richard Paul Fink crept through the second act with reliable artistry, and tenor Rodell Rosel, as Mime, embodied the slippery part with a special deviousness in his voice, which, I imagine can sound equally sweet given the talent he displayed. The part of Fafner felt far too short for the mountainous bass instrument that belongs to Italian Andrea Silvestrelli.

It was Christine Goerke, as Brünnhilde, whom I waited to hear again with the most anticipation. Rising slowly from the raked silver disc that had circled her in flames in Die Walküre, Goerke manifested the role. Brünnhilde has to transform, face an identity crisis, and give in to love in the space of a scene. Essentially, she does what Siegfried accomplishes in a fraction of the time. Goerke has an undeniable presence on stage – that talent that can’t be taught – and a remarkable instrument, more robust and strapping than you would expect from a soprano. Her voice soars with gravity; unshakable and fiercely passionate, she is the ideal Brünnhilde.

What is the Ring without a good orchestra? With conductor and HGO artistic director Patrick Summers on the podium it’s a question you won’t need to ask. Beginning with the iconic sighing bassoons over a tight drum roll, the music pushed and pulled, boiling feeling and anticipation throughout. The brass rang in golden number, the cellos soothed, and the violins, in those terrifyingly exposed unison lines, navigated through the mist like a cicerone. Perhaps the most extravagant show of talent was the French horn that danced its way through Siegfried’s bird-call with pomp and agility.

As dazzling as the production is, La Fura Dels Baus had hits and misses. The assembly line of golden bodies, supernumeraries rolled across the stage suspended by their heels, and the factory farm projections of human embryos sealed in golden eggs, was as shocking and delightfully unsettling as it first was in Das Rheingold. But the second act was a series of disappointments. The dragon was a single line of cold white diamonds locked together in a machine that waved unthreateningly. I wondered if someone got the tail but forget the rest of the body! On the screens at the end of the act, daisies floated, pink and orange and uncomfortable, as the image panned globules of blue drops to the unmistakable outline of a woman’s naked breast and torso, a dismaying visual of the waiting Brünnhilde.

A kiss and a curtain dramatically end Siegfried. After all that has passed, it makes you wonder what will come next – what is to fear in such a love? The small handful of vocal and visual mishaps aside, this production is something astounding in the opera world – rare in its balance of machines and earth, will and destiny. What do we call love? Twilight beckons.