Lily Potter always wanted a daughter but, when she's informed that her daughter is a squib after being informed of the prophecy, she decides that being looked down upon for her gender and possibly raped is just one disadvantage too many. As a result, she insists that James put down "Harry James Potter" for the name, obliviate the midwife, and dig up some kind of artifact which can make their daughter look like a boy.

Circumstances conspire to have her raised in secret by an old house elf and the artifact's ability to hide itself from everyone but the wearer works so well that, by the time little Harry discovers that the artifact can come off, she finds her real face so alien and scary that she promises herself to never take it off again.

Unfortunately, the story goes off onto a temporary tangent part-way through that, while creative, isn't really captivating enough and then hits the limit of what's been written just as the Wizarding World is starting to come back into the picture. (That's why the gender-bending gets demoted to major.)