Mariel Hemingway stars as a Secret Service agent assigned to protect the president's daughter in "First Daughter," a TBS original political thriller premiering Sunday at 8 p.m.

Hemingway's character, reassigned from presidential duty for going against protocol to save the chief executive from an assassination attempt, is called upon to save his daughter, who while on a hiking trip was kidnapped by a revolutionary group.

Monica Keena ("Dawson's Creek") plays the daughter whose life depends on Hemingway and a river guide, portrayed by Doug Savant. Gregory Harrison ("Trapper John, M.D.") plays the president.

Repeats: Sunday at 10 p.m., Saturday at 8:05 p.m. and Sunday, Aug. 22, at 5 p.m.

* Sunday on Showtime at 8 p.m., "The Big Brass Ring," from an original script by Orson Welles and Oja Kodar. In the film, a man's quest for the governorship of Missouri is about to be derailed by a dark family scandal that also threatens his marriage. William Hurt, Miranda Richardson, Nigel Hawthorne and Irene Jacob star. Repeats: Aug. 30 and Sept. 4.

* Sunday on VH1 at 9 p.m., "Sweetwater" represents this network's first venture into original drama. The fact-based story recounts the tuneful but bittersweet story of the band's personal and professional struggles. Nansi Nevins, who disappeared from the limelight after being hit by a drunk driver, served as a film consultant. Amy Jo Johnson, Kelli Williams, Michelle Phillips, Frederic Forrest and Adam Ant play leading roles. Repeats: 11 p.m., Monday at 7 p.m., Wednesday at noon, Thursday at 10 p.m. and Saturday at 4 p.m. VH1's second movie, "Ricky Nelson: Original Teen Idol," is scheduled for Aug. 22.

* Monday-Friday on History Channel at 10 p.m., Peter Coyote narrates the five-part "History of Sex," which sets out to explain what sex has meant to the development of modern civilization and what the development of modern civilization has meant to sex.

The five segments are "The 20th Century" on Monday, "From Don Juan to Queen Victoria" on Tuesday, "The Middle Ages" on Wednesday, "The Eastern World" on Thursday and "Ancient Civilizations" on Friday. Nightly repeats at 2 a.m.

* Thursday and Friday on American Movie Classics at 8 and 8:30 p.m., "The Lot," starring Linda Cardellini, Sara Botsford and Perry Stephens. The two-hour, four-part original story features fictitious movie industry characters set against real and concocted events in the Hollywood of 1937. Two 30-minute episodes air each night. All four air in sequence on Saturday starting at 4 p.m.

* Saturday on TLC at 9 a.m., the start of a 42-hour "Great Books Festival." Two one-hour premieres are included: "Heart of Darkness," Saturday at 10 p.m., and "Dracula," Sunday, Aug. 22, at 10 p.m.

* Saturday on Discovery Channel at 8 p.m., the first of the three-part "Battle of the Sexes" on "Wild Discovery," a series that sets out to explain why so many creatures risk life and limb to reproduce. The first episode, "The Courtship Dance," repeats at midnight. The other two, "The Mating Game" and "The Riddle of Sex," air at the same times on the following two Saturdays.