Karen Nadler is Hal Mason's girlfriend when the series begins. Along with the Masons, she joins the 2nd Massachusetts Militia Regiment. She shows some jealousy toward Lourdes Delgado when she appears interested in Hal.Karen is captured by the aliens in season one, but it's uncertain where her allegiances lie when she is seen again.Background: She was a cheerleader in high school and was spared on the day of the invasion because she cut school to climb a tower and see the spaceship. Her classmates in school all perished.