"Decoding Annie Parker," based on a true story, is an often uneasy, yet sentimental and witty tale of two women, one a cancer patient and the other a geneticist.

Canadian Annie Parker (Samantha Morton) battled breast cancer in the 1970s — and beat it. But after losing her mother and older sister to the disease, she becomes convinced that cancer is stalking her family.

Though most doctors then said cancer was a stroke of bad luck, Annie believes she'll get breast cancer like her immediate family members. Annie checks for lumps daily. And after she discovers one, she must have her left breast removed.

Meanwhile, in Berkeley, California, geneticist Dr. Mary-Claire King (Helen Hunt) is researching genetic links to breast cancer. When Annie learns of this, she starts doing her own research with a medical student and former nurse (Rashida Jones).

Writer-director Steven Bernstein, who was inspired to write "Annie Parker" after reading Parker's unpublished memoir, offsets gloomy moments in the film with ironic humor, as when Annie breaks from oral sex to suggest that she quickly check her husband for testicular cancer.

King, who eventually identified the genetic link to certain types of cancer, spends most of the film ignoring Annie's letters. And Hunt and Morton don't appear onscreen together until the end of the movie, which makes this feel like two projects forced to mingle.

Additionally, Hunt never really displays her talents in this role.

But Bernstein's willingness to show cancer's intense darkness is admirable, though unsettling.

The most harrowing moments of "Decoding Annie Parker" come when a chemo-ridden Annie, having recovered from breast cancer, is suffering from ovarian cancer.

There to support her during much of her illness is her husband, an aspiring musician played by Aaron Paul.

Paul has an extremely simple presence next to the vastly talented Morton, who displays a compelling range of humility, drive and vulnerability.

Having lost most of her hair due to chemo, and with only one breast, Annie struggles to feel desirable. But she manages to maintain a bit of sass, even after she discovers that her husband has been unfaithful.

While talking to herself in the mirror she repeats, "Damn, you're hot. One breast, no hair ... they all want you but they can't have you."