Sean (Josh Hutcherson) is a typical teenage boy who is trying to exert his independence and sometimes acts like he has a chip on his shoulder. At times he is disrespectful and sarcastic, but he has a good heart, and the kid has had it rough; his dad disappeared when Sean was very young. His father is presumed dead, but his body was never found.
Sean's uncle Trevor (Brendan Fraser) is a funny, somewhat irresponsible single male. He has adopted his missing brother's life's work as his own. He is an American college professor and scientist in the field of plate tectonics, and he is committed to continuing the work that he and his brother started, and to finding out what happened to his brother.
Hannah (Anita Briem) is a gorgeous Icelandic mountain guide. She is smart and tough, and she does not take any flak from Trevor and Sean.