"My Sister's Keeper" is a horror movie for parents and a righteous weeper that earns its tears.

Directed with a sure, sensitive hand by Nick Cassavetes ("The Notebook"), it is an actors' showcase built on a moral dilemma. But at its most basic, it's just a good cry.

The Fitzgeralds are coping, through good humor and positive attitude, with a sick child. But we can't see the cost.

Mom (Cameron Diaz) is maniacally focused. Dad (Jason Patric) is a loving breadwinner with a ready smile. But the leukemia that may kill Kate (Sofia Vassilieva) is sucking up all the attention. Brother Jesse (Evan Ellingson) is lost in the vortex of Kate's illness.

Anna, 11 (Abigail Breslin) has had enough. She's the youngest, the child who was "engineered," she narrates, a kid they had who would provide the fetal cells and bone marrow that might give Kate a chance. She may love her sister, but she's willing to hire a lawyer she's seen on TV ( Alec Baldwin) to sue to stop the procedures that dominate her life.

"My Sister's Keeper" has many ways it could go wrong at this point. But Cassavetes, working from a Jodi Picoult novel, never makes a bad move. Sympathies shift as we see what every member of this barely functional family had to deal with for over a decade. The story's structure -- many of the characters narrate their points of view -- moves the film along and leaves room for great acting.

Diaz gives one of the best performances of her career as the "villain" of the piece, an uncompromising fighter. Baldwin is on the money, as always, but so is Breslin, who has turned "Little Miss Sunshine" into a career of character turns that show she can hold her own with the best.

Vassilieva anchors the film with a playful, soulful presence. She makes Kate a real teenager who is keenly aware of what her illness is costing those she loves.

Even the many montages set to mournful pop ballads never cross into maudlin. Cassavetes balances the ethical debate with teenage rites of passage, the grim pallor of death with humor.

Films that present a moral dilemma and make us consider the unthinkable are as rare as bargain popcorn in the summer. Cassavetes manages that feat and turns this weeper into a keeper.