Troubling a Star — Madeleine L'engle

After a year in New York city, Vicky Austin feels restless and totally out of place home in rural Connecticut. Her time away, especially her friendship with Adam Eddington, has changed her.

When Adam's great-aunt Serena gives Vicky a trip to Antarctica as a birthday present, Vicky can't believe her luck. It's a opportunity of a lifetime, and Adam will be working at one of the research stations there.

But the trip is not what Vicky imagined. As she meets her fellow travelers, it quickly becomes clear that some of them are not what they seem. And that her trip into adventure is becoming a journey into icy danger.