Sarah is a young, pretty, confident teenager with a deep faith, and the world seems ready to cater to her wishes. But she hides a warped self-image, depression, and desperate need for self-control, only to force it out in secret purging sessions. As she adjusts to her junior year at a new high school, Sarah struggles to cope with her growing discomfort and self-critical attitudes, even while easily making friends and displaying a confident exterior. One fateful day, Sarah follows her friend's seemingly trivial suggestion and willingly walks into a corrosive world of binging, purging, and depression.

As Sarah leaves for college, she feels increasing pressure from friends to seek help for her bulimia. But college offers a new opportunity to remake herself-if only she doesn't get in her own way. As she struggles to maintain control, she slips further into the darkness and closer to self-destruction. The few strongholds in her life-faith, friends, family, and her dog-keep her together as her heart is battered by broken relationships and her body is abused by her own design.

This novel, based on a true story, follows Sarah as she goes away to college and tries to navigate the difficulties of new adulthood, faces academic struggles, and decides whether to leave bulimia behind or take it with her. Brilliant Disguise narrates a story of a young woman with everything to gain and absolutely everything to lose.