A natural disaster brings half sisters together in British Columbia.It's the last day of 10th grade for Amy when an earthquake hits, shattering windows and collapsing buildings. Her mother is in Japan for business, and her father is working in Vancouver, which is cut off from their small town by freeway damage, but Amy's estranged 17-year-old half sister, Mara, comes to her school to get her. The girls can't reach any of their parents, and since Mara's mom's house has been destroyed, they set off for Amy's but find that it's also uninhabitable. The girls set off on foot with backpacks of emergency supplies, but they encounter aftershocks and heavy rain, among other ordeals. They are welcomed and fed at a Sikh temple, but soon armed soldiers take away all the unaccompanied minors, Amy and Mara included. Feeling something is wrong, they manage to escape. Although the sisters' complex family situation offers an intriguing premise, the character development is too light; Amy states that the earthquake has changed her, but readers don't see enough of her personality before her ordeal to understand how she's different. The nonstop action will draw in the intended audience of reluctant readers, but the abrupt ending doesn't offer any closure. Main characters read white; there is ethnic diversity in the supporting cast.An underdeveloped blend of relationship-driven novel and adventure story. (map) (Fiction. 12-18)