SINGAPORE — What makes a person accountable for a heinous act? Does being not quite right in the head absolve one of the abuse and murder of an innocent child?

Directed by Tracie Pang, this sold-out production of Frozen is Pangdemonium at its darkest and grimmest, luring you into a tragic world of violence, grief, guilt, anger and remorse (or the utter lack of it).

Written by Bryony Lavery and closely based on real-life incidents and characters, the Tony-nominated play features a bizarre triangle. In the middle of which is Ralph (Adrian Pang), a paedophile serial killer convicted of murdering seven girls in 21 years (as a stark reminder, creepy little-girl dresses set up as glowing lanterns hover over the audience like ghosts).

One of the victims is Nancy’s (Karen Tan) daughter Rona (a brief cameo by Tan’s real-life daughter Olivia). The emotional arc of a mother desperately coping with her situation stands in contrast to the clinical perspective of Agnetha (Janice Koh), a psychiatrist obsessed with finding out what makes the criminal mind — including Ralph’s — tick.

Presented primarily as three separate but interlocking character portraits — perhaps echoed by Eucien Chia’s stage set that’s just as broken up and compartmentalised — the three main actors put in exceptional shifts. Despite playing a somewhat underutilised character, Koh offers the occasional burst of dramatic tension. We are also slowly drawn to the internal struggle of Tan’s character — she ages before our eyes, the burden she carries leading to painfully poignant moments, in particular when confronted with her daughter’s remains and, later, the man who caused all this pain.

And that man is wickedly brought to life by Pang. It’s hard to sympathise with a monster like Ralph, but that’s exactly what happens in the actor’s slow-brewing and complete transformation from nonchalant bloke to menacing inmate to despairing soul. His utterly chilling performance as the stuttering, limping predator is, hands down, one of best we’ve seen on stage.

It is to the actors’ credit that Frozen manages to be gripping and engaging, considering the script itself seems rather confused. While there are some truly memorable scenes — mainly the pivotal confrontation between mother and murderer, with the former sharing her family photos as a means of catharsis — it eventually falls short. It erratically sways between medical lecture (literally, in the case of the psychiatrist’s scenes) and human drama as it remains, until a rather weak cop-out ending, undecided on what point it really wants to focus on. Or, for that matter, what kind of play it wants to be (the unflinching psychodrama grit that unfolds is often at odds with the kind of dreamy poetic cadence of some of the lines uttered, which sometimes threw me off).

The stories of the three characters are undoubtedly meant as three different facets or angles in a morbid portrait of evil. I found all three fascinating but stepping back and taking the play in its entirety, it felt as if I was looking at a broken mirror. I came out wishing Frozen had made up its mind on whether it wants to chill us to the bone or warm our hearts.

Frozen runs until Nov 9 at the Esplanade Theatre Studio. Tickets are sold out.