When I was a kid in the late 1970s, my brother and I watched every episode of “Battlestar Galactica,” a campy science fiction show that ran for a single season in 1978-79. It blithely derived its central ideas from diverse sources: the new blockbuster film “Star Wars,” the era’s fascination with Egyptian and other ancient cultures, and even Latter-day Saints theology. I didn’t realize any of those connections at the time, as my brother and I rooted for the Colonials against the robotic Cylons and tried to roll our eyeballs from side to side in imitation of the Cylons’ obsequious (and only) line, “By. Your. Command.”

So it’s not surprising that I also became a fan of the revived “Battlestar Galactica” series more than two decades later. Both programs began with the same premise: a “ragtag fleet” of humans escapes after Cylons unleash a massive nuclear annihilation, destroying the humans’ 12 home planets. But every aspect of the new series was darker than its predecessor. The original series adopted this post-apocalyptic scenario in name only, while actually pursuing a traditional cowboys-and-Indians story line set in outer space. In the postmodern remake, characters realistically battled the kinds of demons survivors would likely face if fewer than 50,000 people had lived through a nuclear holocaust.

One of the most significant changes made by the series was its reconception of Cylon origins. In the first BSG, the Cylons had been created by a reptilian race that conveniently died out centuries ago. That series’ Cylon war was more than a thousand years old, and human beings were merely its hapless victims. In the remake, the Cylons’ creation was far more recent and disturbing: they were “humanity’s children,” created by human beings to do their dirty work and then discarded when the robots evolved and demanded their own rights.

“You cannot play God and then wash your hands of the things that you’ve created,” warned the sage Commander Bill Adama at the revival’s outset. “Sooner or later, the day comes when you can’t hide from the things that you’ve done anymore.” If the original BSG was a hopeful tale of good humans triumphing over soulless killing machines, its revival was a morality play about personal responsibility.

Compared with the original series, the characters in the remake were richly textured and dangerously flawed. Starbuck, who in the 1970s version was a happy-go-lucky but not-so-bright Casanova, was one of the most complex characters in the revival: a female pilot with an almost messianic “special destiny” who was plagued by self-destructive behavior. Scientist Gaius Baltar was a model of self-centeredness despite his genius and the fact that he did, in the end, show some remorse. Further complicating the old facile distinctions between good humans and bad robots, many of the Cylon characters acted nobly and selflessly, and they looked just like human beings, forever blurring the line between person and machine.

But darkness on television is a carefully choreographed dance. Despite BSG’s flawed human characters, it always had someone to root for. While the series raised the question, over and over, whether the human race deserved to survive, it tended to answer in the affirmative. Just in time, there’d be a self-sacrificial moment from the pilot Apollo, Adama’s lone surviving son; or a cry for justice from Helo, a fellow officer who condemned a proposed genocide when the human characters discovered that they had access to a virus that could destroy the Cylons for all time.

The series was filled with tough leadership choices, many falling on the shoulders of Colonial President Laura Roslin. Before the opening episode’s nuclear holocaust, she had been a low-ranking cabinet official with dozens of people ahead of her in line to succeed to the presidency. After all of them were wiped out in the initial attacks, she gamely assumed the mantle of democratic leadership, even though she had just been diagnosed with a fatal cancer.

President Roslin could make tough, controversial leadership calls. Once, she began to steal an election so that the ruthless Baltar would not win the presidency and lead the people into ruin. But guided by her own moral misgivings and the advice of her friend Bill Adama, she decided not to falsify the election results. Baltar was elected and, as predicted, proved to be a disastrous president. Thousands died during his regime. And viewers were left wondering -- which course of action would have been most ethical? What would they have done in Roslin’s place?

Roslin became a great president not only for her refusal to abuse power but because she had a vision -- literally -- of what humanity’s future could be. Once a religious skeptic, she began mining humankind’s old prophecies for guidance about its new future, bravely fulfilling the scriptures’ promise that a “dying leader” would guide the people home to the lost planet Earth.

There’s no Roslin character in the short-lived spinoff series “Caprica,” which began airing its final five episodes on Jan. 4. More’s the pity. There’s also no equivalent to Adama, an aging leader who is grizzled but not jaded, committed to military objectives but not blinded by them. In fact, it’s difficult to know whom, if anyone, to root for on “Caprica,” a leadership void that may explain why the series has been canceled after just one season. “Caprica” has been a strong concept with a scattered execution.

In the second iteration of BSG, human characters were sometimes tried to the breaking point, resulting in avoidable but understandable tragedies, like the heartbreaking suicide of Lt. “Dee” Dualla. But on the prequel “Caprica,” characters also wrestle with tragedy and profound questions about life and death -- the series, after all, investigates the creation of the Cylon prototypes many years before BSG.

Yet viewers have not responded in nearly the same way -- in part because the Syfy channel did a shoddy job with marketing, but mostly because fans have felt alienated by the characters’ nihilism and aimlessness. There is no goal to achieve, no cause to rally around. On BSG, darkness always occurred within the moral framework of how to redeem and prosper humanity. Characters differed on the best way to achieve that goal, but the goal itself was a unifying force. On “Caprica,” human beings wander alone in the darkness, making the darkness impenetrable.

A lesson to viewers is that real leadership matters. Darkness has a legitimate place on television -- no one wants to return to the unthinking camp TV of the 1970s -- but only when it gives viewers all the more reason to cheer. We triumph when characters muscle through tragic circumstances and their own demons to make noble choices, acting with love and courage despite the odds. That’s what’s missing on “Caprica.”

Not surprisingly, Syfy has announced production of a new BSG spinoff series, “Blood and Chrome.” It focuses on the young fighter pilot Bill Adama in the early years of the Cylon wars. It would seem that even in these postmodern days, when viewers are comfortable with the adage that “we have met the enemy, and he is us,” we still need our heroes.