You don't read much about foundlings these days; the word itself has an old-fashioned, vaguely romantic ring to it. The truth is that foundling is just another word for "abandoned child" and Shannon, the protagonist of Marjorie Celona's haunting debut novel, "Y" (Free Press, 259 pages, $24.99), finds nothing romantic about having been left on the doorstop of the YMCA shortly after her birth.

As a baby, she cycles through a succession of foster parents — Raquelle, Julian, Moira, Par — but none of them will commit long-term to Shannon, a child who describes herself as a cross between "Shirley Temple and a pug." After one home changes from unstable to dangerous, Shannon is moved yet again, this time to a foster home that has the feel of a squalid way station, with each child left to fend for herself.

Eventually, Shannon is taken in by Miranda, a single mother who has a daughter named Lydia-Rose who is just Shannon's age. It is not a perfect situation, but it's the best option Shannon has. She and Lydia-Rose form an uneasy alliance, but Lydia-Rose makes it painfully clear to Shannon that there can only be one "real" daughter in the picture.

Along with Shannon's narration of her childhood is the story of her biological parents, told from the shaky borders of her parents' young lives. "In four days my parents will abandon me," says Shannon, "but tonight my parents are childlike and laughing." Yula and Harrison are frightening characters, but Celona skillfully uses Shannon's voice to elicit a sense of empathy for these two lost souls.

As Shannon grows from a painfully self-aware child to an even more uncomfortable adolescent, she can't let go of her visceral need to find her biological family. After running away to Vancouver, she returns to find that Miranda has little tolerance for her teenage rebellion and she is forced to choose between the life she was given and a future, and family, of her own choosing.

Her need to fit in is palpable and heartbreaking. "How do you become a part of one's family?" she asks, "You don't, and you never do." After reconciling with Miranda, she begins her search for her original family in earnest, tracking down the man who first found her that morning on the steps of the Y.

In Shannon, Celona has created an unforgettable heroine, a girl who is navigating the perils of adolescence with the added complications of her indeterminate past. "Y" is both uplifting and devastating to the reader, and in the end, a novel about loss that is nearly impossible to forget.

Meganne Fabrega is a freelance writer and a member of the National Book Critics Circle.