A scene from "Devious Maids" (Lifetime/Lifetime)

British con artists Gwen and Ruby (played by singing YouTube sensations Sophia Grace Brownlee and Rosie McClelland) return to “Sam and Cat” (Nickelodeon at 8 p.m.), slyly trying to drive a wedge between the two best friends.

Sunday talk shows: “Platts Energy Week” (WUSA at 7:30 a.m.) interviews American Enterprise Institute’s Roger Noriega, Inter-American Development Bank’s Ramon Espinasa and McDermott Will & Emory’s Alex Choinski; “This Week in Defense News” (WUSA at 8) has Rear Adm. John Kirby, Professional Services Council’s Alan L Chvotkin and acting Air Force Secretary Eric Fanning; “BioCentury This Week” (WUSA at 8:30) features National Cancer Institute’s Douglas Lowry, Center for Cancer Research’s John T. Schiller, and GlaxoSmithKline Vaccines’ Sophie Biernaux and Joe Cohen; “Fox News Sunday” (Fox at 9) hosts Sens. Ted Cruz (R-Tex.) and Claire McCaskill (D-Mo.) and former U.N. Weapons Inspector Charles Duelfer; “White House Chronicle” (WETA at 9) has Dentons’ Clinton Vince; “State of the Union” (CNN at 9) features Rep. Nancy Pelosi (D-Calif.).

“Newsmakers” (C-SPAN at 10) talks to Rep. Steve Scalise (R-La.); “This Is America & the World” (WETA at 10 and WHUT at 6 p.m.) visits the Royal Opera House Muscat in Oman, and talks to project director Hamid Ghazali, and board of directors members His Highness Sayyid Kamil bin Fahd al Said and Rawya Al Busaidi, minister of higher education; “Meet the Press” (NBC at 10:30) has NRA’s Wayne LaPierre and Sandy Phillips, the mother of an Aurora, Colo., shooting victim; “Face the Nation” (CBS at 10:30) talks to Sens. Joe Manchin (D-W.Va.) and Tom Coburn (R-Okla.) and Rep. Matt Salmon (R-Ariz.); “Bloomberg Government’s Capitol Gains” (Bloomberg TV at 11:30) has Rep. Tim Huelskamp (R-Kan.) and Purdue University’s Mitch Daniels.

Sunday afternoon on “America’s News HQ” (at 4:30), Fox News Channel covers President Obama’s remarks at the memorial service for Navy Yard shooting victims.

Later, E! starts red carpet coverage of the Emmy Awards, with “Live From the Red Carpet: The 2013 Primetime Emmy Awards” (at 6), followed by the awards ceremony, which starts on CBS at 8.

After eight seasons, “Dexter” (Showtime at 9) comes to an end; a preview of the series finale is on Page C1.

AMC has given virtually no description of the episode, but it’s still worth pointing out that it’s the penultimate episode of “Breaking Bad” (AMC at 9).

As the first season of “Devious Maids” (Lifetime at 10) comes to a close, the mystery of who killed Flora is finally resolved.

— Emily Yahr