It's the yin-yang, the perennial agony after the ecstasy for science fiction fans.

Like "Farscape" and "Angel" fans before them, once again, fans are mourning lost favorites or scrambling to save those in dire trouble.

The TV season has begun claiming its scifi victims. It's the pain we fans seemingly must endure year after year.

ABC has canceled "Night Stalker," the second time, as SciFi Wire noted, that the network has killed a series about reporter Carl Kolchak and his pursuit of the supernatural.

Just six episodes of "Night Stalker," an update of the 1974 series, "Kolchak: The Night Stalker," have aired. The original show lasted just one season, from 1974-'75.

The new series, on Thursday nights opposite powerhouses "CSI" and "The Apprentice," struggled in the ratings, falling as low as under 4 million viewers.

It's too late to save "Night Stalker," but will "Threshold" be next?

CBS' entry into the multi-network, alien-invasion derby moves tonight into its new timeslot at 10 p.m. ET and is apparently in trouble and on the bubble. That means it may get picked up, but it might not.

"Threshold" features a talented cast featuring standouts Carla Gugino, Charles S. Dutton, Peter Dinklage, and Brent Spiner. It's the first series to be produced by former Star Trek honcho Brannon Braga.

According to fan reports, the final "Threshold" episode is being filmed and production may wrap at the end of this month if the ratings don't improve and if the network doesn't see solid fan support for the show.

Concerned fans have set up a website, www.ThresholdFans.com, to wage a save-our-show campaign.

I'm dubious many such efforts work; just ask fans of the aforementioned "Angel." But it may be worth a try, especially since "Threshold" is perhaps the best of the new season's crop of new network scifi series.

The best idea, however, I'm sure fans will agree, is simply to make sure to remember to watch "Threshold" in its new time slot tonight and next week, to demonstrate to CBS execs that folks do turn out to watch the show.

It's just a shame that, year-after-year, it comes down to these guerrilla fan campaigns to save science fiction on television.

In the case of "Threshold," the show started out on Friday nights. No series will attract big, broadcast-sized ratings on Fridays. (Even SciFi Channel's successful Friday lineup still gets numbers that look paltry by broadcast standards.)

Therefore, Fridays seemed a perfect night for a niche series like "Threshold" to survive on an evening of lower viewing expectations.

Alas, lower expectations may not be good enough even for good scifi.

A former entertainment journalist, Scott Nance is a member of the USS Chesapeake, an independent science-fiction and Star Trek club in the Washington, D.C., area. He is a columnist for Airlock Alpha, and can be reached at scottnance@airlockalpha.com.