One of the great mysteries of the universe is why Geraldine Quinn is not a superstar. Her intensely powerful singing voice carries range and emotion, wrapped in a compelling cabaret showmanship, full of strut, passion and control.

The seeds of her career on stage were, we learn here, planted at the 1991 Talent Quest in St John’s Regional College, Dandenong, where she and her brother Nick took first place with an ambitious jazz number. Music became a calling for her, later adding comedy into the mix, but he instead chose a more normal career – until his tragic early death from brain cancer.

The Passion of St Nicholas is a warm tribute to him, the ‘golden child’ of the sizeable Quinn family adored by all those who knew him, as well as touching on topics including sibling dynamics and the vagaries of life in the arts.

It’s difficult to criticise a cathartic show on such an intensely personal topic, and Quinn clearly puts herself through the emotional grinder to some extent, despite reassuring audiences that she’s happy that this is a way to ‘get Nick back for an hour every night’.

But on a theatrical basis, there are issues, primarily because the audience don’t get a full picture of who Nick was to better understand their relationship. ‘Perfect’ is a thin character description and we don’t - for example – get a sense of what he felt about his decision to pursue a more stable life over showbiz, which would better contextualise his life, let alone a key dramatic point in the narrative. 

Comparisons with Ed Byrne’s show Tragedy Plus Time, also in the Malthouse Theatre and also about the early death of a sibling are hard to avoid, but the Irish comic paints a more three-dimensional portrait of his late brother and their sometimes fractious relationship, which gives it added depth.

Quinn is more at home putting herself at the centre of the narrative, from how she felt winning the school talent contest at the centre of this narrative to how ill-equipped she was to take the news of his death.

Now, a few years on, she is better placed to process her grief through this collection of anecdotes, touching interludes and kick-ass musical numbers, which are always a festival highlight. Inevitably, this is not all funny, but ultimately, comedy is the lens through which Quinn focuses most of her feelings.

Given the subject matter, it’s probably no surprise The Passion of St Nicholas is more wryly amusing than laugh-out-loud, though the jaunty Oliver!-style song questioning why he couldn’t have died of anything funnier hits a note of particularly glorious gallows humour. It is a celebration, not a wake, after all.

That mood is set by Quinn’s colossal performance skills and towering stage presence – always spellbinding – and her scat jazz interlude is possibly worth the ticket price alone. To consider Nick’s talent could have been on a par with this makes you wonder what the world has missed.

• Geraldine Quinn: The Passion of Saint Nicholas has now finished its Melbourne run.