'Grimm': Adalind makes a big discovery at 9 p.m. on NBC. (Scott Green/NBC)

“Dateline NBC” (NBC at 8 p.m.) tells the story of two sisters who, after their mother died mysteriously, found out what really happened by looking where their mother had told them to look — their baby pictures.

A cybercriminal traps Eliot in an elevator and it’s up to Carrie to save him before they both suffer major consequences on “Unforgettable” (CBS at 8).

“Shark Tank: Swimming With Sharks” (ABC at 8) reports on how some of the show’s favorite products have developed since the founders first pitched the sharks, including the likes of Lollacup, Bubba’s Boneless Ribs and Tree-T-Pee.

Chef Ramsay is in Redondo Beach, Calif., to save Zayna Flaming Grill, a Mediterranean-style joint plagued by mediocre fare and owners, on “Kitchen Nightmares” (Fox at 8).

“Shark Tank” (ABC at 9) hears pitches for a commerce flower business, anti-aging lifting strips, a breakaway hanger and tablewear made from renewable plant materials.

Nick and Hank play tour guides to Trubel and pick up a murder investigation along the way on “Grimm” (NBC at 9).

The death of an undercover detective in Danny’s precinct reveals a big secret on “Blue Bloods” (CBS at 10).

Hannibal continues to lure Will onto the dark side on “Hannibal” (NBC at 10), and that makes Jack suspicious of Will’s intentions and past.

Comedian D.L. Hughley takes the stage at the Regency Theatre in San Francisco to riff on everything from Colorado legalizing marijuana to the value of having noisy neighbors on his one-hour stand-up special “D.L. Hughley: Clear” (Showtime at 10).

Actor Kevin Spacey and comedian Lewis Black stop by “The Tonight Show Starring Jimmy Fallon” (NBC at 11:35).

Comedians Don Rickles and Carmen Lynch are on the “Late Show With David Letterman” (CBS at 11:35), along with a musical performance from the Ghost of a Saber Tooth Tiger.

Actress Julie Bowen and comedian Dave Attell come to “Jimmy Kimmel Live” (ABC at 11:35), with music from Cut Copy.

“The Improv: 50 Years Behind the Brick Wall” (Comedy Central at midnight) gives a retrospective view of 50 years of The Improv, a popular and hugely formative New York comedy club and then comedy club franchise helmed by Budd Friedman. The one-hour special includes interviews with Judd Apatow, Lewis Black, Sarah Silverman and more, along with lots of archive footage from its legendary stand-up stage.

Rachel Lubitz