It was a desire for mates that prompted the Angloans—known as Andromedans by Earth people—to make contact with humans, and the mail order bride program was an attempt to satisfy the needs of the colony they had established on Elios. Much against her will, Liberty Carter and her sister, Lisa, are among the first small group to leave Earth, but Liberty didn't actually want to take part in it. She just couldn't convince Lisa not to go. Or the Angloan, Ravan, who came after her when she failed to show at the space port.