“Supernatural”: Jared Padalecki as Sam and Jensen Ackles as Dean. (Liane Hentscher/The CW)

“The Vampire Diaries” spinoff “The Originals” (CW at 8 p.m.) got a cushy, post-“TVD” time slot last week for the premiere, but now it debuts in its regular time slot, as Rebekah heads to New Orleans to see what’s up with Klaus and Hayley.

You know Twitter is a big deal when the “NCIS” (NBC at 8) agents use it to solve a missing persons case; later, McGee loses his badge, but chooses not to tell his boss.

Jake develops a crush on a medical examiner (guest star Mary Elizabeth Ellis) during an investigation on “Brooklyn Nine Nine” (Fox at 8:30), but his fling winds up having a negative impact on the case.

The controversial PBS documentary “League of Denial: The NFL’s Concussion Crisis” — controversial in the sense that ESPN dropped out of the project after seeing the trailer — debuts Tuesday night on WETA and MPT at 9. In the two-hour “Frontline” special, journalists Steve Fainaru and Mark Fainaru-Wada investigate how thousands of football players claim that the National Football League has covered up results in long-term brain injuries, including early onset dementia and brain damage.

RETURNING SHOW: The unstoppable sci-fi drama “Supernatural” (CW at 9) rolls on to Season 9, but it starts on a tragic note when doctors pronounce an unconscious Sam on the verge of death. As a result, his brother, Dean, frantically calls out to area angels for help — but in exchange, Dean will owe an angel a very big favor when he wakes up.

Schmidt swore revenge on new couple Jess and Nick when they let it slip that he was cheating on his girlfriend on “New Girl” (Fox at 9), so this week, Schmidt sets out to break up the happy pair.

Hillary lies to her parents when she secretly meets up with her crush on “Trophy Wife” (ABC at 9), so Diane and Pete dig for information the best way they know how — on their daughter’s Facebook page.

Comedian Seth Meyers, actor Michael Fassbender and musical guest Amos Lee are on “Late Show With David Letterman” (CBS at 11:35).

Billy Crystal is on “The Tonight Show With Jay Leno” (NBC at 11:35), along with reality stars Snooki and JWoww (Jennifer Farley), and musical guests Toni Braxton and Kenny “Babyface” Edmonds.

“Jimmy Kimmel Live” (ABC at 11:35) hosts actress Emily VanCamp and musical guest Elton John.

— Emily Yahr