Australian playwright Tom Holloway’s drama, first premiered in Australia, and brought to the Fringe here by Hampstead Theatre, has all the highly charged, emotional, ethical, and moral, dilemmas at the heart of it that you’d expect from a play dealing with euthanasia.

It is also achingly heart-breaking on a human level, though some audiences may find the tone- the show starts off intensely and continues in the same vein throughout- too relentlessly one note. However, for me that’s the play’s great strength: it grabs you right from the off and refuses to let go or offer up any respite or release:  much in the same way that there is none for the characters on stage as they face up to the grim reality of their situation.

It opens with Don sitting on a chair near his wife Pam’s bedside, while she lies down reminiscing about a camping holiday they took with the kids years ago that he struggles to recall.

His mind clearly preoccupied with other matters, (hands folding and unfolding; a stroke of his head here, a nervous twitch there), his nerves are jangling for all to see, and as they chat it becomes clear that he is keeping a vigil. Tonight is the night that Pam, who has been diagnosed with terminal cancer has decided to take her own life, and all they can both do now is wait for the drugs she took to end her life to kick in.

It’s a subject we see discussed, and argued over in flashback on Ben Leveson’s simple revolve set- a bed; a chair; a kitchen table; a door- that allows the action to gravely, and gracefully, move back and forth in time.

Heart-wrenching without being sentimental, one of the most interesting things about Holloway’s play is not the ethical arguments pro and con for euthanasia on show, but the human dynamic between this clearly loving couple. Don, who is against the idea but reluctantly goes along with it, sees Pam’s condition and proposed solution as their problem; Pam hers.

Both attitudes  are, in their own way, selfish, and both right. “This isn’t just about you. This is about me too. This is about us, “ rails Don, who views his wife’s decision from the viewpoint of someone  being left, and being left alone. “ Pam, for her part, can only see that she is the one who is dying, the one who will never see the kids get married, never get to read a book or see a film again. “You’re going to get to do all of that, and I’m being selfish?” she says.

Paterson, breath-taking in his portrayal of confused, grasping at straws naked vulnerability,, and Molloy, stoic and resolute, deliver an acting master-class here. If there are two better performances to be seen on this year’s Fringe I’ll be surprised.

By the end it was all I could do not to join in with the woman seated in front of me, in bursting into floods of tears.Make sure you take a hankie; no make that a box.

And No More Shall We Part, Traverse Theatre, Edinburgh until Aug 26.. Tel :0131 228 1404