John Patrick Shanley has an impressive resume to his name. As the Oscar-winning writer of films such as Moonstruck and Joe Versus The Volcano, you might know him best as the scribe behind the Tony award-winning Doubt: A Parable. Catholic guilt plays a big role in a lot of Shanley’s writing and one of his earliest works, 1983’s Danny and the Deep Blue Sea, is no exception. Theatrum Veritatus are currently presenting the play at Theatre N16, and though this is a very powerful and moving production, it is let down by a script that will just not let up on the monotony.

Danny (Gareth O’Connor) and Roberta (Megan Lloyd-Jones) are two tortured souls, who happen upon each other one night in a New York bar. He’s furious, violent, called “The Beast” by his colleagues. She’s a depressed single mother with Catholic parents. From initial encounter to the next morning, we track their relationship through distrust, guilt and an overwhelming sense of love neither feel they are entitled to. Danny and the Deep Blue Sea really is more of a character study than a play, and these characters are always going to give fascinating reactions to each other. They blame themselves because that’s how they’ve been brought up, and it’s very unnerving to watch them both self-destruct in front of your eyes.

That said, this is a story where nothing happens, no-one changes and everything interesting about these characters happens off-stage. What Danny and the Deep Blue Sea boils down to is two people sitting in bed, telling each other things that might happen. That’s hardly compelling theatre, and though I can admire the explosive nature of this relationship, I can’t engage in it because nobody is achieving anything. You wish the play would jump ahead a couple of days, just to add some life – what has been said has been said, but still Shanley continues to batter you round the head with the same message. It leaves the 80-minute production feeling a lot longer than it actually is. Don’t expect a satisfying ending either.

O’Connor and Lloyd-Jones give powerful performances, but they can tend to shout a lot. O’Connor has some very explosive reactions at times, only some of them earned. When Danny softens, this brings out the skill in O’Connor’s work: his warm persona fills the stage and brings out some of the more emotional moments towards the play’s end. Lloyd-Jones gives a brilliant performance at times – she’s tough yet nurturing – but her accent needs work. It takes the character explaining her Italian-American roots before we have any idea where she’s from.

Visually, director Courtney Larkin isn’t given much opportunity to roll her sleeves up as the action is so static. There is, however, an excellent movement sequence used to explore the graphic, violent and slightly erotic nature of the couple’s love-making. It is skilfully choreographed and impressively performed by our actors, but a shame we don’t get more moments like this, as they could have lifted the dreary nature of the script and sent it into more interesting heights.

This is a savage, mean and depressing slog of a play. If you’re in the mood for being bashed around the head by a sea of unrelenting parables, then you’ll have a great time. Personally I found it very hard to engage, despite the committed performances from O’Connor and Lloyd-Jones. This is far from what the great John Patrick Shanley can do.

Danny and the Deep Blue Sea is playing at Theatre N16 until 14 April. For more information visit the Theatre N16 website.