Warning: Wikipedia contains spoilers
At the rendezvous, the Cylons attacked the unsuspecting ships and destroyed all of them except for the Galactica. Commander Adama of the Galactica had already been suspicious of this uncharacteristic peace offer, and was the only one to put his ship on battle alert after his sons Apollo and Zac found the attack force on patrol. Realizing that the home worlds were now vulnerable, he withdrew to intervene, only to learn that the Cylons had already devastated them.
With the human colony civilization in ruins, Commander Adama proposed the only chance for humanity to survive. He would lead a refugee fleet in search of the lost human colony, a planet known only as Earth. Thus, with the Galactica leading a ragtag fleet of ships of every variety and state of repair, Adama with the help of his second, Colonel Tigh and his best fighter pilots, his surviving son Apollo, and the hotshot pilot, Starbuck, search for that planet. Unfortunately, the Cylons are in determined pursuit. The Cylon Imperious Leader, however, is displeased with Baltar's part of the deal and orders him sought and executed (at least in the theatrical version of the pilot).
The fleet finds brief haven on the resort planet of Carillon. Meanwhile, our heroes discover a trap with the Cylons plotting to turn over the entire population of the fleet to the Ovions. Starbuck and Apollo, while rescuing their fellow comrades, set fire to the tylium mine below which will cause the planet to self-destruct at a certain point in time. The humans escape, the fleet battles the Cylons, and Starbuck & Apollo manage to intercept the Cylon Base Star before Carillon is destroyed. The rag-tag fleet continues their quest for Earth.
In the uncut television version of the pilot, there is an epilogue in which Baltar's life is spared, thus setting the stage for the series to come.
The balance of the series followed the fleet on their journey. The series is also noted for its references to Mormonism.
Synopsis of the original pilot film
The show is set in a distant part of outer space in what is disclosed as "the seventh millennium of time". There, the human colonies had been fighting a thousand-year war against the mechanoid Cylons who sought to exterminate humanity. The series began with the Cylons suing for peace thanks to the diplomatic efforts of human councilor Baltar. In reality, he had betrayed humanity for personal power by leading the fleet of the main ships of the line, giant fighter carriers called Battlestars, into a trap.Broadcast History
Original
The pilot to this series, the biggest budgeted of that time, originally was released theatrically in Canada and Europe in the summer of 1978 in a 125-minute version, and in most cases outgrossed "Star Wars" in terms of box-office receipts. Months later, in September, the uncut 148-minute pilot premiered on ABC with spectacular ratings, but as the series continued they slid as the writing declined and the budget restrictions meant that the established special effects shots were overplayed into tedium. Star Wars creator George Lucas sued the producers for plagiarism, and in April of 1979 the network executives cancelled the still strong-rated show in a failed attempt to position Mork and Mindy into a more lucrative time slot. A month later, the theatrical version of the pilot was finally released to U.S. theatres.Galactica 1980
A sequel series, called Galactica 1980, in which the fleet found and protected Earth, was a quick failure due to its low budget, widely-panned writing, and ill-placed time slot (Sundays at 7:00 PM, a time slot generally reserved for family-oriented programming and news shows).Revival Attempts
However, the original show has maintained a cult fandom ever since which support competing efforts by Glen Larson and Richard Hatch to revive the premise.2003 miniseries
Universal Studios produced a "re-imagining" of the theme concepts for the Sci Fi Channel, debuted December 8, 2003. The term "re-imagining" was used to indicate that it was not simply a remake of the original but a new direction taken from the same original premises.