Once you buy into legends about 13th-century knights protecting deep, divine secrets with mind-blowing implications for modern man, nothing seems too preposterous. So viewers of the four-hour miniseries “The Last Templar” (8 p.m., Sunday and Monday, NBC) will be predisposed to accept a scene of four horsemen clad in Crusader gear galloping through Manhattan traffic and breaking into a New York museum to steal rare Vatican artifacts right from under the noses of Champagne-sipping celebrities wearing tuxedos and evening gowns.

Once you swallow this story of a globe-spanning search for an ancient decoder, a secret map, hidden treasure and an earth-shattering secret, you’ll have no problem accepting Mira Sorvino as Tess Chaykin, a famous archeologist and daughter of the world’s most famous treasure hunter. But don’t think she’s merely a workaholic covered in the dust of ancient pyramids. She’s all woman. More than that, she’s a girly girl, given to form-fitting dresses and obsessed with name-brand footwear.

• It doesn’t seem possible that Sigourney Weaver has never appeared in a made-for-TV movie before. She debuts in “Prayers for Bobby” (8 p.m., today, Lifetime) as Mary Griffiths, a devout California wife and mother whose unbending sense of scripture divides her from her sensitive son, Bobby (Ryan Kelley), after he announces that he has homosexual feelings.

Set in the late 1970s in Northern California, the film presents the Griffiths as a loving working-class family with faith at the center of their lives. Bobby confides his anguish and doubts to his athletic older brother, Ed (Austin Nichols), who feels compelled to share them with mom.

While the film never condescends to its characters, Weaver’s turn as scripture-spouting Mary seems more brittle than believable. In fact, the film tries so hard to be fair to Mary and Bobby that it reduces both to cardboard cutouts. Mary is the perfectly correct Christian, and Bobby is the perfectly misunderstood boy who becomes a perfect martyr when his alienation from his faith and his family drives him to suicide. This trauma inspires Mary to become the perfect crusader for greater understanding.

In this earnest drama, Mary’s elderly mother stands out as a flesh-and-blood character. She’s viciously homophobic, but she doesn’t single out gay people. She’s mad at everyone and mean about everything, the way some real people can be when they’re not symbolic players in an afternoon special or a Lifetime movie. She’s a “real character” in both senses of the term, and “Bobby” could use a few more like her.

Today’s highlights

• Viewers can catch up with the first four seasons of “Lost” (7 p.m., ABC) before watching the two-hour, season 5 premiere (8 p.m.).

• Mario Lopez hosts the 2009 Miss America Pageant (7 p.m., TLC) live from Las Vegas.

• Sam Neill stars in the 2006 fantasy “Merlin’s Apprentice” (6 p.m., Sci Fi).

Sunday’s highlights

• Lisa meets her mental match on “The Simpsons” (7 p.m., Fox).

• A handsome doctor (Adam Kaufman) follows an ancient edict to marry the childless widow (Lauren Ambrose) of his deceased brother in the TV movie “Loving Leah” (8 p.m., CBS).