The Vampire Diaries: Isobel (guest star Mia Kirshner) is back on a new episode of the supernatural drama (8 p.m. KTLA).
American Idol: Season 4 contestant Constantine Maroulis performs on the talent competition's results show (8 p.m. Fox).
The Bear Whisperer: Steve Searles tries to prove he's smarter than the average, well, you know, in this new nature series (10 p.m. Animal Planet).
The Real Housewives of New York City: The Big Apple edition of the reality franchise is back (10 p.m. Bravo).
Mounted in Alaska: A taxidermy shop is the setting for this new reality series (10 and 10:30 p.m. History).
Apocalypse 2012: Survivalists share their preparations for the prophesied end of the world (6, 7, 9 and 10 p.m. CNBC).
Into Iceland's Volcano: Scientists visit the geologically active island nation (6 and 9 p.m. National Geographic), followed by the similarly themed special "Man vs. Volcano" (7 and 10 p.m.).
Unfaithful: Stories of Betrayal: Infidelity is topic A in this new special (10 p.m. OWN).
Frankenstein: Colin Clive is the doctor and Boris Karloff is his creation in this 1931 horror classic (7 p.m. TCM), and Ian McKellen portrays "Frankenstein" director James Whale in the 1998 bio-pic "Gods and Monsters" (10 p.m. Sundance).
Golf: The Masters tournament gets underway in Augusta, Ga. (noon ESPN).
Basketball: The Celtics battle the Bulls (5 p.m. TNT) and the Trail Blazers visit the Jazz (7:30 p.m. TNT).