Maggie Gyllenhaal shines as an ex-convict rebuilding her life, writes Michael Dwyer

NONE of the many US independent productions released here this year has proved as arresting or as thought-provoking as Half Nelsonand Sherrybaby. Both deal with the increasingly messy lives of young middle-class losers whose hopes and ambitions are undermined by a self-destructive nature rooted in their drug addiction. And each of the two films is powered by a vivid central performance that gradually encourages the viewer to care for and worry about its complicated protagonist - Ryan Gosling as the troubled teacher in Half Nelsonand Maggie Gyllenhaal playing an insecure ex-convict in Sherrybaby.

Her character, Sherry Swanson, is 23 when released on parole after serving a three-year sentence for robbery to feed her addiction. "From when I was 16 to 22, heroin was the love of my life," she says. Now clean and sober for over two years, she longs to be reunited with the true love of her life, her young daughter (Ryan Simpkins), who has been in the care of her brother (Brad William Henke) and his wife (Bridget Barkan). They have become closely attached to the child and worry about the consequences of Sherry regaining custody.

Several incidents threaten Sherry's precarious new stability, one involving an aggressive inhabitant of the halfway house where she is placed, another a reunion with her father that prompts unsettling suggestions about their relationship. And we learn that Sherry worked as a stripper called Lolita when she was 16, and that she is quite willing to use her body to get what she wants.

Writer-director Laurie Collyer, who makes her narrative feature debut on Sherrybabyafter working in documentaries, ends the movie on a dedication: "For Sue". The inspiration for the film, Sue was a close childhood friend who went to prison the year Collyer graduated from college.

While Collyer's view of her Sherry creation is essentially sympathetic, she never shrinks from confronting the character's volatility and irresponsibility. Sherry has an entirely unpredictable personality, being a victim of her own past and now her own worst enemy. Yet, for all her experience of hard knocks at such a young age, she remains immature. We get to know Sherry intimately in every salient detail.

In her bravest, most adventurous performance since Secretary, Gyllenhaal immerses herself in the role so completely that we share Collyer's caring for Sherry as a brittle young woman caught between human frailty and her own best intentions. Gyllenhaal strikes a magnetic screen presence, seamlessly blending aching tenderness and terrific vitality from beginning to end of this touching, unsparing moral drama.