Having picked a character from the pages of Hudson's Bay Company history for Isobel Gunn, her preceding novel about a woman who disguises herself as man in order to work in the fur trade, Audrey Thomas has deftly plucked a character from Charles Dickens for Tattycoram (Penguin, $29.95), a second penetrating novel about a relatively powerless woman struggling with her identity.

It's not necessary to untangle the lines between fictional reality (Dickens) and fictionalized fiction (Thomas) in order to read Tattycoram, but the twin realms make for an intriguing comparison.

In the Dickens' novel Little Dorrit, an insular English gentleman named Meagles magnanimously rescues a girl named Harriet Beadle from the Foundling Hospital, an institution that arose in imitation of the hospital for "found children"; in Paris. Established in 1739, the original Foundling Hospital in London was sponsored by a retired seaman, Thomas Coram.

"Harriet we changed into Hattie,"; explains Mr. Meagles, "and then into Tatty, because, as practical people, we thought even a playful name might be a new thing to her, and might have a softening and affectionate kind of effect, don't you see?"; By applying the nickname Tattycoram, the do-gooder Meagles and his daughter effectively ensure their maid will never be able to conceal her disreputable beginnings.

The Thomas novel tells it differently. After infancy in a caring foster home, our heroine Hattie is mired in the Foundling Hospital from ages five to fifteen, until hard-luck Hattie gains domestic employment in the household of Dickens.

The great author dotes on her and encourages her to read books from his library, much to the resentment of Dickens' sister-in-law Georgina, who trains a parrot to tauntingly repeat the nickname Tattycoram. Then Hattie escapes servitude by running off with a Miss Wade in what can be perceived as a veiled lesbian relationship,

Thomas has Hattie marry her foster brother-only to have her happiness and security interrupted decades later by the news that Dickens has caricatured in her Little Dorrit. Having been stuck with the nickname Tattycoram was bad enough, but now Hattie must decide whether or not her ex-employer has taken advantage of her by stealing her identity for his work.

Should she risk confronting the great man? A fellow orphan named Elisabeth urges Hattie to take umbrage but Hattie is less accusatory and more worldly. "It's not nice, what he's done, but he understands my resentment,"; she concludes, "and he understands about foundlings and children born out of wedlock."; 0-86492-431-3