William Shakespeare’s play “Winter’s Tale” includes the most famous and laughed-over bit of stage direction ever composed: “Exit, pursued by a bear.”

That line could also sum up the grim final installments of “Grizzly Man Diaries” (8 p.m., Animal Planet). As followers of this series already know, self-educated naturalist Timothy Treadwell spent years documenting his life among wild grizzly bears in remote Alaska.

Tonight’s episode, “The Fall,” is filled with foreboding comments by the normally chipper Treadwell. He stands by longtime bear companion Quincy and praises him for not eating him during a period of near starvation. He cheerfully tells his video diary that becoming Quincy’s meal would have been perfectly natural, and he even embroiders his resigned ruminations on self-sacrifice with a proverb inspired from the New Testament: “Live by the sword; die by the sword.” I always suspected that Treadwell saw himself as a Christ figure to his ursine companions, and this line only confirms my suspicions. Though in Treadwell’s case, it probably should read: “Live by the video camera; die by the video camera.”

Few suspect that Quincy ended Treadwell’s expedition and his life. In the naturalist’s final tapes, we see an older and malnourished bear arrive. Treadwell dubs this confused newcomer Oly, and his final video diaries follow Oly’s difficult and at times violent interaction with Treadwell’s neighbors.

¢ Jim Lehrer moderates a debate between presidential candidates John McCain and Barack Obama (8 p.m., ABC, CBS, NBC, PBS, CNN, Fox News, MSNBC, BBC America, CSPAN, Telemundo) live from the University of Mississippi in Oxford, Miss.

Tonight’s other highlights

Note: Listings may vary due to local sports coverage.

¢ Photographer William Klein spoofs the high-fashion world in the 1966 satire “Who Are You, Polly Maggoo?” (6 p.m., Sundance), starring Dorothy MacGowan as an American model in Paris.

¢ Scheduled on “20/20” (7 p.m., ABC): Diane Sawyer interviews Sens. John McCain and Barack Obama as well as their respective wives, Cindy McCain and Michelle Obama.

¢ A former TV psychic (Simon Baker) renounces his profession and becomes an adviser to a police homicide squad on the pilot episode of “The Mentalist” (7 p.m., CBS).

¢ Contestants pretend to work and we pretend to care on “America’s Toughest Jobs” (7 p.m., NBC).

¢ Olympic favorites Nastia Liukin, Shawn Johnson, Alicia Sacramone and many others make their first post Beijing TV appearances on “2008 Tour of Gymnastics Superstars” (7 p.m., MYNetwork).

¢ Zack, Cody and London embark on a cruise ship in the spin-off series “Suite Life on Deck: The Suite Life Sets Sail” (7 p.m., Disney).

¢ Rescue and redemption on two episodes of “The Dog Whisperer” (7 p.m. and 7:30 p.m., National Geographic).

¢ “World’s Creepiest Destinations” (8 p.m., Travel) visits the Lizzie Borden Bed and Breakfast and other tourist destinations with grim pedigrees.

¢ Jackson visits Atlantis on “Stargate Atlantis” (9 p.m., Sci Fi).