SIR David McVicar is waiting for me in a rehearsal room engulfed in greys. Grey mock pillars, grey flooring. The set for his new production of Debussy’s Pelleas and Melisande – which opens at Scottish Opera tomorrow – is inspired by the paintings of Vilhelm Hammershoi, an enigmatic Danish artist whose late 19th century portraits are layered in grey upon grey. When Hammershoi thought one of his works wasn’t quite grey enough, he would add another wash across the surface: more grey.

“It’s just a stepping off point,” McVicar warns me when I start to ask about visual-musical parallels. “It’s not like we’re slavishly recreating Hammershoi paintings or the singers are doing Hammershoi poses. It’s simply a visual correlation for the way I feel about the music. The sense of mystery. If there are subjects in the paintings, they’re often looking away from the viewer. Half-open doors, a sense that you don’t know what’s happening in the other room but you’re certain something is happening in the other room.”

Debussy’s 1902 opera is not grey, but there is much that is hidden from view. The libretto is from Maurice Maeterlink’s symbolist play about a toxic love triangle: Golaud discovers the mysterious Melisande lost and traumatised in the forest; he takes her home to the cheerless castle ruled by his grandfather Arkel and they marry, but soon his young bride develops feelings for his younger half-brother Pelleas and things spiral. The atmosphere in this family is dank and noxious; the characters are damaged and lonely and unable to communicate. There is always more that is unsaid than said, more unsung than sung, and Debussy’s lush, limpid orchestration swirls around the vocal lines like a thick mist that the characters can’t see through. If they feel lost in their fetid, half-lit world, the audience feels even more so.

McVicar bemoans a common practice of projecting all that narrative murk into lack of clarity when it comes to performance. “I’ve seen productions where everyone is playing symbols, but as an actor you can’t play a symbol,” he says, looking mildly irate at the notion. “You can only play a character in a story. You have to be incredibly specific about everything you do on stage: why you’re there, why you’re interacting, otherwise the whole thing becomes so lacking in intrinsic energy. You don’t have to announce the decisions actors are making – that can remain illusive and elusive, but the actors themselves have to know precisely what’s going on.”

Glasgow-born McVicar is known internationally as a director who doesn’t flinch from the violent and the lewd. If you saw his 2012 Scottish Opera production of The Rake’s Progress you’ll probably recall the brothel scene, a carnival of garish burlesque replete with dildos and dominatrix in which Mother Goose milked her own giant breasts and fed the juice around. Elsewhere, McVicar has cut to the stark violence at the heart of Aida, the grim power play in Rigoletto.

Where will he take an opera in which abuse and disfunction are so latent and ambiguous? He talks about giving the characters motivation: “A lot of women are asked to be vague when they’re playing Melisande, to be a cypher for the male characters to project onto, but I don’t think that’s useful. She has to have wants and needs of her own.” He talks about “a strong spiritual dimension to the story, in the sense of the soul’s contact with corporal reality and how that inevitably damages and corrupts.”

Mostly he talks about the cyclical nature of the characters’ behaviour. “Golaud is not intrinsically bad. It’s just as he says himself: 'Je suis perdu moi-meme.’” When I suggest the men in the opera have always struck me as pretty monstrous, McVicar eyes me wearily and reaches for his iPad. “Look,” he sighs. “The whole symbolist movement kicked off with this poem called Correspondences by Charles Baudelaire. He uses the forest as a metaphor for the world.” He waits for me to read through the poem; I feel like I’m back in a undergraduate French exam, my Parisian professeure grimacing every time I botched a pluperfect or failed to translate the wit of Andre Breton.

“The characters,” McVicar spells out. “They’re all spiritual beings lost in a dark world that they can’t quite understand. It makes them behave in ways that damages others and themselves. But that’s just the journey of life. It’s not only this particular family. There’s a big clue in the fact that Arkel is the king of Allemonde – that’s not exactly a subtle symbol! The name of the country is ‘all the world’. It’s a very pessimistic piece, but it’s a very tender piece.”

Does he find any hope in it? “No!” he almost shouts, exasperated. “There’s no hope! Sorry, I’m not going to offer you a way out. I can’t dish up comfort. I’m not an agony aunt. It’s not the Barber of Seville, what can I do? At times of contentment and plenty the Barber of Seville is appropriate. Not now.”

There does seem, I venture, a timely message in the way that fear and incomprehension and a sense of helplessness in the face of external events can start to corrode our own moral compasses and personal relationships.

“God yes!” he exhales. “World events are inevitably feeding into this because we’re artists. We’re making a good piece of art, and any good piece of art is intrinsically political, even if it doesn’t announce itself. We’re watching this tragic circus unfolding across the Atlantic and none of us is recognising the country we ourselves live in at the moment. That sense of sadness and trying to understand how lives can get so off-kilter – it’s informing our work every single day.”

And yet the world of Pelleas and Melisande is inescapably interior: it’s an everywhere disconnected from anywhere. “Right,” he nods. “And that is exactly why I called it a spiritual world. It’s a world of introspection. And in such frightening political times, I think introspection is valuable for all of us to retain our humanity. It’s also periods like this when the meaning of art becomes so important. We have to believe in what we’re doing because putting people in touch with their spirituality is so important.”

“Does any of us achieve a happy ending? Course not. It’s how we live the journey. It’s how tender or abusive we can be to each other. The choices that we make. And it’s time like now that we need to think really hard about what makes us good human beings, and what makes the journey from the cradle to the grave worthwhile.” He pauses and, for the first time in our interview, he smiles. “Now that is a hopeful thing.”

Pelleas and Melisande opens at the Theatre Royal, Glasgow, tomorrow