When The Knot of the Heart premiered at the Almeida Theatre in Islington last month it was reportedly so harrowing that some members of the audience were forced to walk out, with one woman even fainting.

Seeing the play - about a young middle-class TV presenter-turned heroin addict - for myself this week, I wondered if I was watching the same production that so shocked its opening audience.

For while David Eldridge's latest offering has strong acting across the board and a slick set design, the dialogue often feels contrived and repetitive.

Lucy (played by Lisa Dillon in a role specifically written for her) is a 27-year-old children's TV presenter and the play opens with her feeding a burgeoning heroin addiction in mother Barbara's (played by Margot Leicester) luxurious Islington garden.

As the precocious Lucy bullies her desperately well-meaning mum into helping her light up, she admits to recently losing her job after BBC bosses catch her indulging her smack addiction.

Over the next three years we follow Lucy's battle with drug dependency, a hellish journey that drags her through prostitution, hospital, a crisis centre and finally, rather oddly, epiphany in South Africa.

It is only after uncovering the roots of her relationship with her suffocating, pathetic mother and hard-nosed, cold solicitor sister Angela (played by Abigail Crittenden) that Lucy can finally come to terms with her addiction.

However, this revelation - "The big thing. That no one ever talked about. How Daddy died" – comes late in the second half and feels like a rushed and convenient way of explaining away Lucy's predicament.

The most dramatic events – Lucy's prostitution in Clissold Park, her kidnapping by dealers and the deaths of fellow 'travelers' – are only ever spoken about rather than acted, robbing them of their impact and resulting in fairly repetitive responses to trauma.

And while this helps focus the play on Lucy's interaction with her mother – usually involving clutching each other and crying – the writing is much more engaging when it lives in the present, such as when a dodgy TV executive tries to pull the wool over Lucy's eyes or when her mother finds her using needles for the first time.

However, both Lisa Dillon and Margot Leicester put in strong performances (with Lisa showing incredible stamina, remaining on the stage almost entirely throughout the two-and-a-half hours) and Kieran Bew nails his many varied male roles, from camp nurse to spun-out addict.

Ultimately though, this feels like a sanitised vision of heroin addiction, written specifically for the N1 audience it portrays.