Mozart's Idomeneo, rè di Creta is a sprawling monster of an opera; messy in its misappropriations of classical myth, and chaotic in the pacing and development of its plot, it fills a long evening by being strangely voluminous in parts and curiously bare in others. Gone are the taut sexual dynamics of Le nozze di Figaro, or the relentless impetus towards destruction of Don Giovanni; yet Idomeneo's subtly anarchist undertones follow the instincts of both those operas, challenging and problematising accepted feudal power structures in favour of a true meritocracy where virtue and nobility will go hand in hand into a braver, better future. Mozart turns to tragic peril as his emotional engine for Idomeneo, thrusting his characters into ever more miserable social and emotional plights before dragging them to a gruesome finale where the failure of the old world is just as prominent as the triumph of the new.

As a result, it's been an tempting target for Regietheater in recent times, but director Tim Albery has tried to produce a relatively straightforward and sensible Idomeneo for Garsington; peopled by sensible fisherfolk in oilskins and wellies, with principals in 18th-century silk, there's not a rubber shark or stormtrooper in sight. The key question for any director, how to embody Neptune's vengeance on Crete on the stage, is translated by Albery into a plague which causes members of the chorus to vomit dark blue blood from their mouths before being zipped into bodybags and dumped in a shipping container; this all works nicely until Idamante goes off to defeat the disease with his sword, at which point the analogy falls down and the silliness peeps through.

]This is the problem with Idomeneo: you can spend a lot of time and energy trying to love it, but fundamentally its characters are more ciphers than people. It certainly isn't difficult to care for this production's exceptionally affecting Ilia from Louise Alder, whose softly iridescent soprano constantly impresses. Her "Zefiretti" aria soared calmly across the pattering of rainstorms outside on a thoroughly wet night at Wormsley. Nor is it hard to take an interest in Caitlin Hulcup's youthful, humble and charming Idamante, beautifully voiced and played with affecting innocence and nicely masculine body language. And, opening on the evening of Father's Day, the scenes of recognition and dismay between Idomeneo and Idamante seemed to thrum with a special poignancy, as did Ilia's pathetic attempts to claim Idomeneo as a second father, and Elettra's desperate need to be loved by anyone at all.

In fact, Rebecca von Lipinski's exceptionally dramatic, angry and vulnerable Elettra was a treat to watch throughout the evening; even if the risks she took with her timing and phrasing didn't always pay off, there was an indomitably vibrant energy to von Lipinski's performance, and a wholehearted enthusiasm in her approach, which made Elettra's final, cataclysmic psychological breakdown truly moving. As a defeated Elettra left the stage, weeping, the whole opera paused while her sobs echoed across the silence: a haunting moment.

The smaller roles are exceptionally well voiced. Timothy Robinson makes a charismatic, warmly sung Arbace – his "Sventurata Sidon" is gorgeously expressive and rich in tone and emotion. Robert Murray's High Priest has a wonderful sense of urgency and fateful accusation. A fabulously oil-bespattered Neptune from Nicholas Masters is just as impressive for his sudden, electrifying appearance as for his sumptuous bass.

Idomeneo himself is sung by Toby Spence, whose light lyric tenor never quite felt heroic enough for this pagan king. This Idomeneo didn't really make a journey from cruelty to enlightenment, more a bus ride from weak leadership to inadequate fatherhood, and finally irrelevance. Spence's voice did open up and take control in the very final scenes, and may settle into something much more impressive over the course of the run, but on opening night he didn't seem to own the role or the stage, despite some skilful acting.

Hannah Clark's brutalist design of a slanting stage made of slatted planks, with two shipping containers, one half-sunk as if shipwrecked in sand, made for a simple, dramatic backdrop with a brilliantly built-in earthquake (you'll see what I mean when you get there). The Garsington Opera Orchestra, conducted by Tobias Ringborg, kept the music flowing, and generally the balance between singers and orchestra was good. In all, an admirable attempt to straighten out Idomeneo; but maybe this particular mythical beast would actually benefit more from a little fire in the belly.