NOW IN ITS fourth season, “Grantchester” on “Masterpiece Theater” (9 p.m. Sunday, PBS, TV-14, check local listings) is undergoing a changing of the guard. What are the chances that the stunning English scenery will produce two handsome, crime-fighting vicars?

As fans of the show know, “Grantchester” is set in the bucolic countryside around Cambridge, England, in the mid-1950s. The series stars Robson Green as hard-boiled police detective Geordie Keating, who has partnered with the local Anglican priest, Sidney Chambers (James Norton).

Their partnership in crime-fighting has allowed them to contrast their very different worldviews. Sidney is very taken with jazz and beautiful women, and a little too fond of drinking. He seems excited to be living in a time of change, of jet planes and Elvis Presley. Geordie, a war veteran and conservative dad, thinks the world is on its way to ruin. And with dead bodies popping up on a regular basis, who can blame him?

Over the course of this season, Sidney will be written out of the proceedings, making room for Tom Brittney (“Outlander,” “Call the Midwife”) as Rev. Will Davenport, Geordie’s new clerical sidekick.

But first, Sidney and “Grantchester” explore another facet of changing times in 1950s Cambridge, when a delegation of black American ministers and civil rights activists arrive on a speaking tour.

Needless to say, threats, controversy, murder and romance ensue. This all seems a bit on the nose, not to mention strange, given that Great Britain had its own version of racial strife at the time. But “Grantchester” isn’t history; it’s television, complete with the distractions of great architecture, gardens and landscapes. The season opener would be better if it didn’t combine two hourlong episodes into a single two-hour helping.

• TLC offers a new twist on the spate of programs observing the 20th anniversary of the tragic death of John F. Kennedy Jr., as well as those of his wife and sister-in-law. Rather than dwell on the fateful plane crash, “JFK Jr. and Carolyn’s Wedding: The Lost Tapes” (8 p.m. Saturday) essentially rehashes the well-chronicled history of the late Camelot-linked couple and unspools personal videotape of their nuptials, along with commentary from people who were there and from authors and experts who’ve written on the couple in the past two decades. Nothing screams “exciting Saturday night” like watching somebody else’s wedding video! Particularly when they’re dead!

• Subject to many changes and imitations over its 27 seasons, “Top Gear” (8 p.m. Sunday, BBC America, TV-14) returns, with host Chris Harris joined by cricket star Andrew ‘Freddie’ Flintoff and comedian Paddy McGuinness. Over the course of the season, they will compare electric cars, visit the world’s largest motorcycle show and go on an epic road trip to Ethiopia.

• Imitation being the sincerest form of television, National Geographic kicks off a weeklong SharkFest (not to be confused with Discovery’s Shark Week), with “When Sharks Attack” (9 p.m. Sunday, TV-14).

Saturday highlights

• MLB action (7 p.m., Fox).

• Vin Diesel stars in the 2015 sequel “Furious 7” (8 p.m., NBC, TV-14).

• A creep assumes the identity of a sleep expert in the 2019 shocker “Stalked by My Doctor: A Sleepwalker’s Nightmare” (8 p.m., Lifetime, TV-14).

• The 2018 fantasy “Fantastic Beasts: The Crimes of Grindelwald” (8 p.m., HBO) continues the mythical, magical saga conjured up by author J.K. Rowling.

• “Planet Earth” (9 p.m., BBC America, TV-PG) showcases the world’s deadliest animal predators on “Best of the Hunt.”

• Remembered for its disco soundtrack and its luminous star, John Travolta, the popular dance spectacle “Saturday Night Fever” (9 p.m., Sundance, TV-14) paints a bleak portrait of urban life, circa 1977.

• Lacey Chabert hosts “2019 Christmas: A First Look Preview Special” (10 p.m., Hallmark, TV-G), a glance at the mistletoe onslaught to come.

Sunday highlights

• Scheduled on “60 Minutes” (7 p.m., CBS, TV-PG): China’s embrace of AI; a YouTube star and best-selling author deals with obsessive-compulsive disorder; Italian chef Massimo Bottura.

• New evidence on “Burden of Truth” (8 p.m., CW, TV-PG).

• A custody battle turns deadly on “Instinct” (9 p.m., CBS, TV-14).

• Enemy territory on “The 100” (9 p.m., CW, r, TV-14).

• Morgan focuses on the big picture on “Fear the Walking Dead” (9 p.m., AMC, TV-MA).

• Teresa May’s days of facing “Prime Minister’s Questions” (9 p.m., r, C-SPAN) are coming to an end.

• Mary Louise surprises Celeste on “Big Little Lies” (9 p.m., HBO, TV-MA).

• Forensic evidence proves elusive on “City on a Hill” (9 p.m., Showtime, TV-MA)

• A law firm lawyers up on “The Good Fight” (10 p.m., CBS, TV-MA).

• A blizzard cripples the city on “New Amsterdam” (10 p.m., NBC, r, TV-14).

• A free spirit crosses paths with the wrong sort on the premiere of the docuseries “Impact of Murder” (10 p.m., ID, TV-14).

• Roger’s misbehavior continues as his network trains its focus on the newly elected Barack Obama on “The Loudest Voice” (10 p.m., Showtime, TV-MA).

Cult choice

A researcher (Katharine Hepburn) balks at the expert (Spencer Tracy) whom she fears may replace her with a computer in the 1957 romantic comedy “Desk Set” (10 p.m. Sunday, TCM, TV-G).

Saturday series

Tim Tebow hosts “Million Dollar Mile” (8 p.m., CBS, TV-G) ... Down Argentine way on “Shark Tank” (8 p.m., ABC, r, TV-PG) ... Two helpings of “48 Hours,” the second hour a repeat (9 p.m., CBS) ... “Press Your Luck” (9 p.m., ABC, r, TV-PG) ... “Card Sharks” (10 p.m., ABC, r, TV-PG).

Sunday series

Julie Chen Moonves hosts “Big Brother” (8 p.m., CBS, TV-PG) ... Auditions continue on “America’s Got Talent” (8 p.m., NBC, r, TV-PG) ... High-tech temptations on “The Simpsons” (8 p.m., Fox, r, TV-PG) ... “Celebrity Family Feud” (8 p.m., ABC, TV-PG) ... A killer app on “Bob’s Burgers” (8:30 p.m., Fox, r, TV-PG).

Clearing the heir on “Family Guy” (9 p.m., Fox, r, TV-14) ... “The $100,000 Pyramid” (9 p.m., ABC, TV-14) ... Ken Jeong and Fred Willard appear on “What Just Happened??!” (9:30 p.m., Fox, TV-PG) ... “To Tell the Truth” (10 p.m., ABC, TV-14).