(All times Eastern.)
Riverdale (CW at 8) Jughead learns some of Riverdale's shocking history when he talks to Toni's grandfather.
Dynasty (CW at 9) When Fallon is taken hostage, the family has to try to rescue her.
9-1-1 (Fox at 9) A plane crash leaves Bobby and the team with a slew of patients, and Athena wants revenge against teen bullies.
The Assassination of Gianni Versace: American Crime Story (FX at 10) Andrew Cunanan comes to Miami with the intention of stalking Versace.
David Attenborough's Great Barrier Reef (Smithsonian at 8) The nature veteran examines Earth's largest living structure.
Let's Get Physical (Pop TV at 8:30) Matt Jones stars as middle-aged slacker Joe Force, who inherits a fitness movement and gym from his father.
The Real Housewives of New Jersey (Bravo at 9) Reunion Part 2.
Schitt's Creek (Pop at 8) Season 4.
Conan (TBS at 11) DJ Khaled, Natasha Leggero, the Ghost of Paul Revere.
Daily Show (Comedy Central at 11) P.K. Subban.
Fallon (NBC at 11:34) Ice-T, Meghan Trainor, the Avett Brothers.
Colbert (CBS at 11:35) Willem Dafoe, RuPaul, Roy Wood Jr.
Kimmel (ABC at 11:35) Lisa Kudrow, Rich Eisen, Bahamas.
Meyers (NBC at 12:37) Jim Gaffigan, Van Jones, Josh Gondelman, Brann Dailor.