A believer and an agnostic walk into a room. That sounds like the setup for an existential joke — and not unlike the premise for “The Sunset Limited” (8 p.m., HBO), an adaptation of a play by Pulitzer Prize-winning novelist Cormac McCarthy.

Tommy Lee Jones stars as a gruff college professor who has just tried to end his life by throwing himself in front of the subway train that gives this play and movie its name. Samuel L. Jackson is the deeply religious man who saved his life.

As the film begins, both men are seated at a kitchen table in a tenement apartment where they hash out matters of life and death, God and godlessness, hope and despair. Such subjects lend themselves to performances best appreciated in the intimacy of the theater.

• On a more prosaic note, the 2011 shocker “Iron Invader” (8 p.m., SyFy) mulls the possibilities of a crashing meteorite introducing alien bacteria to an industrial junkyard where the will to survive manifests itself in a giant metal monster. Kavan Smith (“Eureka,” “Red: Werewolf Hunter”), Nicole de Boer (“Dead Zone,” “Stargate: Atlantis”) and Donnelly Rhodes (“Battlestar Galactica,” “Tron: Legacy”) star.

• Animal lovers should take out time from rewatching the YouTube “Pug Attack” commercial from last week’s Super Bowl and check out the new series “Must Love Cats” (7 p.m., Animal Planet), devoted to profiles of felines in all of their glory. We meet hero cats and talented tabbies.

Host John Fulton goes on the road to visit cat-only hotels and other purr-fectly ridiculous places.

Tonight’s other highlights

• NASCAR racing (7 p.m., Fox).

• Jennie Garth, Ethan Erickson, Marilu Henner and Fred Willard star in the 2011 romantic comedy “Accidentally in Love” (8 p.m., Hallmark).

• Check out “For The Love of Movies: The Story of American Film Criticism” (7 p.m., Documentary Channel). There’s no way I’m panning a film about critics.

• Nikki Blonsky stars in the 2007 adaptation of the Broadway musical “Hairspray,” (8 p.m., ABC), itself an adaptation of John Waters’ 1988 film comedy.

• Weddings and other time warps on “Primeval” (8 p.m., BBC America).

• Scheduled on “48 Hours Mystery” (9 p.m., CBS): a dog trainer to the stars, a pack leader no longer.

• John Cleese appears on “The Graham Norton Show” (9 p.m., BBC America).

• Russell Brand hosts “Saturday Night Live” (10:30 p.m., NBC), featuring musical guest Chris Brown.

Series notes

An agent needs help on “NCIS: Los Angeles” (7 p.m., CBS) … A troubling tandem on “Harry’s Law” (8 p.m., NBC) … A killer on the loose on “CSI: Miami” (8 p.m., CBS) … Sunny, with a chance of homicide on “Law & Order: Los Angeles” (8 p.m., NBC) … Maria Bello guest stars on “Law & Order: SVU” (9 p.m., NBC).