When Cass, 14, arrives to spend Christmas vacation with the grandparents she hasn't seen or heard from since her dad's funeral 11 years ago, she's taken aback to find that Grandfather is reserved, even taciturn, while Grandma, apparently unwell, is equally uncommunicative. Moreover, their Arizona trailer park doesn't welcome kids, and Cass learns something her grandparents don't know: the rules state that she must leave by New Year's, though her ticket home is a week later. Meanwhile, Cass and Jordy, another 14-year-old visitor to the camp, have struck up an uneasy friendship despite their prickly sensitivities: Jordy, who is brooding over his parents' recent divorce, also has trouble dealing with his diabetes; Cass, whose immature mom is enjoying the holidays with ""her latest jock-boyfriend,"" is embarrassed by being overweight. Jordy, already an experienced activist, solves the eviction threat with a petition and some well-timed publicity; then, in a well-orchestrated climax, Cass saves his life when he has a diabetic attack on a hike, leading to healthier self-acceptance on both sides and some touching revelations about Cass's grandparents, who have always cared for her more than they were able to show. Sinykin's writing isn't seamless, but she captures--with painful accuracy--a teen's touchy blend of protective defiance and vulnerable competence while presenting two likable young people getting to know themselves and each other in an unusual context.