One of the leading ladies of TV science fiction returns tonight in a new series. For 10 years on “Stargate SG-1” and one season on its spinoff, “Stargate: Atlantis,” Amanda Tapping played the brilliant Col. Samantha Carter. Now she’s back, out of uniform and in a new role.

On “Sanctuary,” debuting at 9 tonight on Sci Fi, Tapping plays another brainy scientist, Dr. Helen Magnus. The Brit leads a group that collects what she calls “abnormals” and others would call monsters.

Magnus is aided in this mission by her reckless daughter, Ashley (played by Emilie Ullerup), and tech wiz Henry (Ryan Robbins). In the two-hour opener, she recruits skeptical forensic psychiatrist Dr. Will Zimmerman (Robin Dunne), whom she has met in the past.

There are those who seek to scuttle this sanctuary, led by John Druitt (Christopher Heyerdahl).

“Sanctuary” has the distinction of being the only series to shoot extensively on green screen using extraordinary visual effects and virtual sets. This allows it to get a big-budget look with cable dollars.

While its opener has a distinctive feel, the question is where does “Sanctuary” go from there? Does it just find a different bogeyman every week for its menagerie? If there’s an overarching mythology, it isn’t readily apparent yet. Also, the characters must develop further than their current stereotypes. The show’s direction needs to be clearer if it hopes to capture enough viewers to thrive like Tapping’s previous series.

A second show premiering tonight shows a different side of Elizabeth Reaser.

Reaser, best known for her recurring role of hard-luck patient Ava/Rebecca on “Grey’s Anatomy,” embraces the lighter role of Bella Bloom on “The Ex-List,” debuting at 9 on CBS.

Bella is a carefree thirtysomething who owns a flower shop and is a serial dater who is taking her time to find Mr. Right.

That is, until she visits a psychic during the bachelorette party for her younger sister, Daphne (played by Rachel Boston). There she is told that she has already met her soul mate, and that she has one year to find him again or be alone for the rest of her life.

So Bella starts making a list of exes, guided by the psychic, who suggests that she follow obvious signs. The series, based on an Israeli program, follows her misadventures through her former romances, in an effort to find “the one.”

Reaser is winning as Bella, and she has a strong supporting cast. But will the audience for “The Ex-List” be home on Friday night, or will they be out trying to find their own soul mate?