If monsters aren’t real then why do we tell so many stories about them? When the menacing shadow of actor Peter Coonan stretches large across the opening of Ross Dungan’s new play for the 15th Oak theatre company, covering a girl (Zena Donnelly) playing piano in the after hours, we might suspect the child to have descended into a dark bedtime story. It turns out Coonan is no boogeyman but in fact her father, David, who tells a story to unnerve her during an emergency taking place in their town: the discovery of a missing girl’s body.

David’s story holds brighter outcomes. Two brothers who own a town in France are at war with each other when one’s daughter goes missing. After the town is torn apart, the girl returns and reminds them that when she took her first step it was both their hands she held on to. Peace is restored. They live happily ever after.

Later on, David enquires to his father Vincent (Lorcan Cranitch) about the truth in the tale. “It’s a myth”, he chortles. In the evolution of narrative from fact to fiction and vice versa, we sometimes find it hard to know what to believe.

On first impression we’re not sure if Dungan, whose pen has often lavished dense narration and novelistic detail, is content with letting his characters take their place in the drama or assume the role of storyteller themselves. Not that the latter has wielded entirely bad results – the epistolary epic The Life and Sorta Death of Eric Argyle built into an affecting crescendo where characters perished powerfully into prose. However, it becomes clear that Before Monsters Were Made marks a significant departure into dialogue for the playwright, and with it comes the realisation that in lieu of crowding the onlooker with details, what’s left unsaid is just as tantalising.

The action, underscored by constant suspicion by director Ben Kidd, plays in elegant décors enclosed by earth and fallen furniture in Zia Holly’s design, suggesting a blasted domestic scene. There is a sense of suppressed hostility under the clicking of cutlery during a lengthy family dinner, as David’s wife Abigail (Orla Fitzgerald) questions Vincent about the strange events surrounding him since the young girl’s death. His spouse Jackie (Janice Byrne) and other son Graham (Manus Halligan) angrily dismiss her insinuations for the rumours they’ll generate: “That’s just something to fill the empty air”.

Measured to great suspense by Kidd, the action is especially grounded by Fitzgerald, whose naturalistic turn introduces bold statements that never feel like departures or exaggerations. Coonan, you can sense, is well controlled, leaving us to wonder if he’ll unleash that raw power that the actor is known for in his screen roles. The master player here is Cranitch, the stylistic stresses of his voice and disciplined gestures giving him ownership of the stage when given free reign. He holds the guessing audience in the palm of his hand until the last moment.

As the drama hurtles towards its conclusion, the playwright manages to problematise every narrative smartly, leaving us to sort through a conspiracy theory, an alibi and a questionable bedtime story. However, the terror in this mystery play lies not in the truth of our tales but in the truths we choose to believe. As the heartbreak of Halligan’s performance in the final crushing moments testifies, this a stealthy drama about the ruinous effects of myth-making, what they conceal and what they tarnish. After all, in the end what survives are the stories people tell, whether they be about fathers, daughters or monsters.

Before Monsters Were Made is playing at the Project Arts Centre until 16 May. For more information and tickets, see the Project Arts Centre website.