Eighteen-year-old high school senior, Sheila Munroe, has always taken her role as big sister seriously. However, one day her younger sister, Maggie, shares a shocking confidence with Sheila, one which is part truth and part deception. The lie not only implicates Sheila in a gruesome murder but also uncovers an appalling secret. While Detective Sergeant Mickey MacKinnon and his team investigate the murder of a local celebrity, Sheila pursues a campaign of her own in an attempt to unravel the mystery surrounding her sister's deceit. It soon becomes apparent that the two investigations have interests in common, and Sheila learns that she is not only a murder suspect but also the target of a killer.