This miniseries follows the lives of three families affected by contact with aliens: The Clarkes, the Keys and the Crawfords.
For the Clarkes it begins when Sally Clarke finds a stranger hiding out in her shed. She brings him in and looks after him, falling in love with him. She realises there is something strange about him and, eventually, he tells her that he is an alien, being hunted down by the government after his ship crash-landed. Even though she is married -- her husband is away -- she and John make love. John has to leave as Sally's son has betrayed him but he promises to come back for her one day. She discovers later that she is pregnant with his child - Jacob - the first human/alien hybrid.
The story continues through several generations of these families until the birth of a perfect hybrid - Allie, John's great granddaughter, the daughter of his granddaughter, Lisa and Charlie Keys - brings events to a head.
John returns to help his great granddaughter, explaining why the aliens have been coming to Earth and experimenting on humans. He gives her the greatest gift -- the means to hide all the Taken (alien abductees) from the aliens by destroying the locators in each one.