Prisoners couldn’t wait to get out of the place, but since closing in 1963, the island penitentiary Alcatraz has attracted countless visitors and hosted many events, including the 100th episode — a live version — of “Ghost Hunters” (8 p.m., Syfy). Look for Jason, Grant and the usual crew as well as “Ghost Hunters International” hosts Barry FitzGerald and Dustin Pari. This spectral spectacular puts a whole new spin on the term “crossover episode.”

And if two hours of bumps in the night aren’t enough for you, Syfy.com will stream an “Aftershow” beginning at 11 p.m. Or is that an afterglow?

• Connections of a different sort loom large on “The Locator” (9 p.m., WE), now entering its fourth season. Scouring legal records and employing gumshoe techniques, Troy Dunn helps reconnect adult children with their biological parents and siblings separated by adoption, divorce or more unusual circumstances. Since 1990, he has found more than 40,000 people.

“The Locator” is emotional television, making the most of its subjects’ long-buried sense of loss. And the culminating “reveals” rarely unfold without someone, or everyone, breaking down. If easy tears are your cup of tea, then “The Locator” has no equal. Tonight, Dunn helps a woman named Dawn find the father she always called “Apple Daddy,” a man who walked out on Dawn and her mother 35 years ago.

• Barbara Walters recently announced that Sunday’s Oscar-night special, her 29th, would be her last. Fear not: I have a feeling there is a replacement in the wings. “The Oprah Winfrey Oscar Special” (9 p.m., ABC) offers interviews with stars and celebrities who either stand to take home a gold statuette on Sunday night or who had a brush with Oscar in years past.

Guests include Penelope Cruz, Halle Berry, James Cameron, Ben Affleck, Sigourney Weaver, Glenn Close and Michael Douglas. Oprah presides over this gathering more as den mother than interviewer, allowing her guests to ask questions of one another. So Cameron sits down with “Avatar” stars Weaver, Sam Worthington and Zoe Saldana, while Close and Douglas recall the phenomenon that was “Fatal Attraction.”

• “Web Soup” (7 p.m., G4) returns for a third season of odd clips from the Internet accompanied by snarky commentary from host Chris Hardwick.

Tonight’s other highlights

• Veronica’s unannounced road trip sparks concern on “Mercy” (7 p.m. NBC).

• The top-10 men sing to survive on “American Idol” (7 p.m., Fox).

• Kathy Griffin guest stars as a community activist on “Law & Order: Special Victims Unit” (8 p.m., NBC). In a second episode (9 p.m.), two murders strike an emotional chord with Benson.

• Fears confronted on “Modern Family” (8 p.m., ABC).

• An ax-wielding suspect is just the beginning on “CSI: NY” (9 p.m., CBS).

• Tales of a shark attack seem fishy on “Psych” (9 p.m., USA).

• A trip to the future ties up some loose ends on “Being Erica” (9 p.m., SoapNet).

Cult choice

Combining computer imagery and the feel of a graphic novel, the 2006 adventure “300” (8 p.m., TNT) offers a hyper-violent take on the battle of Thermopylae.