Battlestar Galactica

Warning: This show plot contains several spoilers—if you have not seen the show, you have been warned!

Decades after the conclusion of the Cylon War, in which the robotic Cylons rebelled against their human creators, the Cylons return to the human settlements of the Twelve Colonies to exact their revenge. This time, they have created thirteen humanoid Cylons models, seven of which have infiltrated humanity, enabling them to annihilate the Colonies. 

A human fleet of survivors, led by the only remaining military ship, the Battlestar Galactica, flies through the cosmos trying to evade the Cylons and find a new home. Over time, Galactica's commander, William Adama, has to deal with political issues, Cylon infiltrators, dissension in the fleet, and numerous other problems. Eventually, the fleet finds a hospitable planet, but the Cylons find them there and chase them away. After the final five Cylons realize who they are, the fleet allies itself with rebellious Cylons who want to give humanity a chance. 

Together, they find the fabled Earth, where a thirteenth tribe of humanity was said to have settled, but it turns out to have been populated by the original Cylons, of which the final five Cylons were a few, and long since destroyed. When Hera, the child of Karl "Helo" Agathon and Sharon "Athena" Agathon and the only Cylon-human hybrid, is taken by the leader of the Cylons, Brother Cavil, to be examined, Adama leads a rescue attempt and destroys the remaining antagonistic Cylons. 

Ace pilot Kara "Starbuck" Thrace, who had mysteriously died and returned to life, finds the way to another, far safer planet through the musical notes of a song, where the survivors of humanity and the Cylons settle. This Earth is revealed to be the Earth we live on today, and Hera is the person from whom all living humans in modern times are descended. The series' events are guided by mysterious messengers of a being or beings that some call God, though its true nature is never revealed.