Bryony Lavery's remarkable play, seen four years ago at Birmingham Rep, tackles a notoriously treacherous subject: our attitudes to crime and punishment, and in particular to the treatment of child-abusing serial killers.
But it is a measure of her sensitivity that she manages to overcome both her heroine's, and our own, instinctive loathing and hatred.
Lavery introduces her three characters through interwoven monologue. Nancy is the grieving mother who, over 20 years, slowly and painfully comes to terms with the disappearance and murder of her 10-year-old daughter. Ralph is the killer who, we eventually learn, has abducted seven young girls and talks of his "centre of operations". And Agnetha is the American-Icelandic criminal psychologist who comes to England to lecture on the subject of serial killers and study the imprisoned Ralph.
Striking is the dramatic use Lavery makes of her central metaphor. Agnetha, who views serial killing as a form of illness rather than of evil, talks of "the frozen arctic sea that is the criminal brain".
Nancy spends much of her time in a state of frozen hate until, partly under the influence of her surviving daughter, she learns to embrace life and forgive her daughter's killer.
Even the psychologist, haunted by the death of her professional partner, seems to exist in a condition of chilly clinical exactitude.
The force of Lavery's play, however, lies in its ability to change hearts and minds. It never mitigates the horror of child killing, but it makes us understand Agnetha's argument that physical damage to the brain, rather than inborn evil, prompts serial murder.
In an extraordinary scene, Nancy confronts Ralph in his cell and offers him a forgiveness far more fatal than a distant cold-blooded revenge.
I still think there are contradictions within Lavery's argument: on one level she is out to prove the predictable banality of the killer, yet Agnetha describes Ralph as "mesmerising like a rattlesnake". And, while showing Ralph as methodically calculating, Lavery brushes aside the idea of moral responsibility. But, in a world filled with tabloid hysteria, Lavery's play comes across as a refreshing draught of sanity. It is also flawlessly acted in Bill Alexander's austere Cottesloe production.
Anita Dobson, an underrated actress, brilliantly charts Nancy's progress from frozen emptiness to thawed humanity. Tom Georgeson no less powerfully shows Ralph as a damaged figure grappling with the concept of remorse. Josie Lawrence conveys the sadness that underlies the professional detachment of the psychologist.
Greeted with pin-drop silence, this is a play that genuinely enlarges one's understanding.
· In rep until August 24. Box office: 020-7452 3000.
