Mike Leigh’s “Vera Drake,” a portrait of a loving wife, devoted mother, selfless caregiver and clandestine abortionist, is a powerful but incomplete film.

“Drake” is more of a good-looking ethics debate than a work of art. The film has heart, yet one feels Leigh has sacrificed some amount of subtlety and style, as well as character development, in his determination to force people to consider the many sides of the divisive issue of abortion.

The filmmaker is surely to be commended for his restraint: although it is clear how he feels about the subject, he refrains from engaging in didacticism. But the film might have reached great heights if Leigh had only pulled his gaze away from the ethical issues in question and given his potentially fascinating protagonist the depth she deserves.

The film follows Vera Drake (Imelda Staunton), a middle-aged, working-class denizen of 1950s England. Her sole concern in life, it seems, is ensuring the comfort of those she loves. Drake spends her days cleaning the houses of wealthy employers, and in the evening, she stops by the homes of sick acquaintances and extended family members to adjust their bedclothes and make them tea. Drake busily bustles through life without a thought for her own needs, always with a placid smile of utter contentedness on her face.

We learn of one other important activity in Drake’s life when she opens a little cloth bag to reveal a suction hose, a syringe, a cheese-grater and a bar of pink soap. About once a week, she visits the houses of desperate young women who find themselves pregnant and unable to care for a child. With the same achingly benevolent manner she uses when fluffing a crippled neighbor’s pillows, she assures these young women that everything will be all right. “You’ve got to help them out,” she says.

As Drake, Staunton is incredible. One can see conflicting emotions in her face with uncanny clarity. Her joy is luminous, her grief jagged and shattering. In many senses, the film doesn’t live up to her performance.

To his credit, Leigh carefully crafts each of Drake’s patients to further his ethical examination. There is a struggling mother of seven who cannot afford to feed another mouth, a young immigrant living in penury, a cocktail-holding glamour girl (who has undergone similar procedures many times), and a guilt-ridden housewife desperate to get rid of evidence of her infidelity.

When one of her patients nearly dies, the police show up at Drake’s home, and in minutes, her life is shattered. Staunton’s portrayal of Drake’s grief at being torn from her family is devastating.

She is taken to the police station and interrogated. It is here that Leigh could explore his heroine’s motivations and inner life, though we are unfortunately denied any close examination. In her distress, Drake barely manages to stammer that she found herself with an unwanted pregnancy at some point in her youth, and she then dissolves into incoherence. Surely a woman who so staunchly supports conventional morality in every other area of her life must have a compelling reason to defy the rigid values of her society regarding abortion.

Even more disappointing than the lack of explanation for Drake’s actions is the lack of disapproval manifested by her family members, her employers and even the police officers who arrest her. No one actually seems angry, a reaction that is unlikely in such a notoriously conservative period of British history.

Furthermore, Leigh’s scrupulous avoidance of any mention of religion seems out of place, if not forced, in a film that so carefully dissects so many social implications of abortion.

“Drake” has all the raw materials of a great film: a riveting protagonist, thoughtful cinematography and provocative subject matter. Had Leigh been a bit less cautious in his presentation of Drake’s story, perhaps the film would have been more effective.