My daughter Ana was born screaming. The youngest of my three girls, she came into this life filled with passionate anger, an offended pride, an unmatched fury.

She vented her infant wrath on all of us, but mostly on me, her mother. This child nursed with a vengeance, stormed through the house like a dervish when she learned to walk, and pitched fits that sent me scurrying from public places in tears.

It felt personal sometimes, like I'd done something grievously wrong, failed some kind of mothering test. Ana's tantrums achieved a sort of notoriety in the family and among our friends. When we moved to a new house, I had to tell the neighbors, "If you hear screaming, I'm not killing the children--it's only Ana." And soon enough, they understood.

By two years of age, Ana had found the dress-up box and laid claim to a black satin clutch, a pair of white opera gloves, a string of faux pearls. We couldn't leave the house without them. One day the gloves went missing, and after a formidable protest, Ana pulled white socks over her hands instead. A pair of plastic children's sunglasses completed her ensemble; she seated herself in the stroller like a movie star settled into her limousine and allowed us to go. For months, we could depart with either the entire ensemble or a colossal tantrum, and frankly it was just easier to let it go. With three children, some victories aren't worth the battle.

When Ana was three, she was expelled from her preschool on the second day for throwing a chair at the teacher. Back at home, she developed an imaginary friend named Jimmy who went everywhere with us. Typically, Jimmy was responsible for any mishap that occurred. When I asked her to describe Jimmy, the picture was unnerving: red skin, yellow eyes, a tail. And some days, as Ana went into a sudden rage, I could more easily believe in demonic possession than I could in the parenting advice I received.

But one year ago, again as a flash from bright to dark, Ana became the morose, the intolerant, the intense screamer of the past. No one could answer for the reversal. Her teacher said nothing was different at school--no seat changes or playground brawls. We hadn't had any upheavals at home, either, to account for the shift.

To me, her mood change felt like the descent of depression, how it settles in like an unwelcome guest and makes itself known. I called the pediatric psychiatrist for a re-check. This time, the answer wasn't a simple "She'll outgrow it." This time, the suggestion was chilling.

The psychiatrist told us, "It may be that Ana has borderline bipolar and obsessive-compulsive disorders." Not one of these potentially debilitating conditions, but both. We're in the process of diagnosing her now. I observe her behavior and report at great length to the therapist; I try to deal with her moods and behaviors. But it's terrifying to me.

Here is my child, seven years old, with the look of an angel on her face and the torment of the devil within her. When she makes a mistake in her schoolwork now, she writes over and over the mistake with darker and darker pencil until the paper shreds. When she gets upset with her artwork, she destroys what may have been hours of work with vengeance. She slaps herself, pulls her hair, and picks at scabs mercilessly. When she gets angry, she rakes her skin with her nails; I keep them trimmed as short as possible. She seems unable to leave the house without her backpack full of dozens of bits and pieces--Barbie shoes, scraps of paper, odds and ends that weigh up to 10 pounds on her small back, never mind the homework or lunch box. It's a behavior called hoarding, a symptom of OCD. Medication is an option we're still exploring; I neither want to rush to it nor decline it out of hand just yet.

"Give her a time out," friends said when Ana kicked into overload. What they didn't realize was that Ana in a time-out zone became a caged animal; everything was dashed from shelves: books, figurines, pictures. In her room, she tore her blankets off her bed and upended toy bins. "What she needs is a good spanking," I heard from annoyed relatives. The few times I tried tough love only made things worse: It enraged Ana to the point where I feared for her safety, and made me feel terrible, besides. "Put her on Ritalin," I was told, but she wasn't hyperactive. I forged onward with her and the rest of my family, winning some days and losing on others.

Then, in the pediatrician's office, I saw a flyer for a child temperament study. I enrolled Ana immediately. I received a thick questionnaire to fill out. A few weeks later, a detailed report arrived, with a follow-up call from a nurse to explain the results.

Ana's temperament profile listed her as highly sensitive and low-adapting. She registered as highly irritable (she was chronically sleep-deprived, yet refused naps and fought sleep some nights until after 11 p.m.). And, no surprise to me, she scored as very high intensity--almost off the scale. The nurse gave me some parenting tips to help with the behaviors. For example, I couldn't just say, "Let's go!" I needed to give her incremental warnings like, "We're leaving in half an hour," "We're leaving pretty soon," and "We're leaving in five minutes." I kept trying.

At about this time, Ana developed an irrational, overwhelming fear of knives. "I think it's going to stab me," she would say of a bread knife left on the counter. Her elfin face was pale with worry. "I'm scared it's going to kill me." She held her small hands to her throat as if to protect herself.

I made an appointment with a child psychiatrist. We met several times, and Ana revealed that she'd seen a scary movie with a knife scene in it--something a baby-sitter had played on the VCR one night when we'd gone out. The psychiatrist concurred with the results of the temperament study but felt that Ana would come along in her own time.

And she did. Suddenly, like the flick of a switch, Ana became another child. We joked that the evil twin had departed and left the good twin behind. We watched and wondered for weeks when the spell would break; who was this wunderkind, this charming, sweet-tempered, angelic child? We switched preschools and she flourished; she learned to swim, went to a summer play program with alacrity, sailed through kindergarten, and began first grade. Ana learned her letters and began to read, and met the academic challenges set before her. She made friends and managed the lunch line without much trouble. I felt pretty confident that the hard times were over with her, and despite her rough start, she was going to be OK.

In the midst of this tumult, I spoke about my child with a Catholic priest, who said to me, "God writes straight with crooked lines." I thought it was incredibly trite when he said it and could barely hide my annoyance. But the idea began to grow on me. I don't believe God punishes us with afflictions but helps us grow through them. I have come to understand that as difficult as it is to accept what dark gifts we are given, this is God's plan for her, and even though I'm her mother, I am not privy to that plan.

Mothering is not a template I can lay over each child to "raise her right" simply by filling in all the requisite blanks. Mothering is a relationship that is constantly evolving. My bond with my eldest daughter is utterly different from the one I have with Ana, and the way I relate to my middle daughter is different from both of the others.

All three girls are the product of a healthy marriage, a financially secure home with strong Catholic faith and values, and a suburban middle-class environment. Yet Ana at seven is so different; she seems to need me so desperately, and I want to protect her from the world, or from herself. We are like each other's anchors--which can either save you and tether you to something safe and good, or drag you under.

It feels as if we are embarking on a dark journey together, but eventually she'll leave me behind and have to go on, in and out of shadows on her own.

So much of her behavior makes sense now--the ups and downs, the insistence on a certain article of clothing. I wish I had known before; I might have been--what? A better mother? I don't know what that means anymore. But we keep going as best we can. And we pray for the mercy in God's plan.