'THE NIGHT SHIFT': Krista (R, played by Jeananne Goosen) comes to the aid of a girl whose parents refuse to acknowledge her eating disorder. (Lewis Jacobs/NBC)

“Time Scanners” (MPT and WETA at 8 p.m.) examines the structural history behind St. Paul’s Cathedral in London. Laser scans give new insight into how the cathedral survived a direct hit from a German bomb during the London Blitz.

It’s Ali’s first day back at Rosewood High on “Pretty Little Liars” (ABC Family at 8), and her return marks the beginning of a long-awaited apology to right her past wrongs with the rest of the girls.

“History Detectives Special Investigations” (MPT and WETA at 9) looks into the disappearance during World War II of popular American bandleader Glenn Miller, who vanished when the airplane carrying him from England to France went off the grid over the English Channel.

The third installment of “The ’90s: The Last Great Decade” (NatGeo at 9) covers the new generations in tech alongside what the nation’s political sex scandals meant for the years to come.

SERIES PREMIERE: Now for your daily dose of reality shows you can’t believe exist: “Married at First Sight” (FYI at 9) introduces viewers to six people who are yearning for a lifelong partnership and agree to get married the first moment they meet a semi-random person who has been screened by four specialists (a sexologist, a spiritual adviser, a psychologist and a sociologist) for compatibility.

SERIES PREMIERE: “Restaurant Startup” (CNBC at 10) is a reality series in which a restaurateur (Joe Bastianich) and a chef (Tim Love) listen to pitches from would-be restaurant owners, who get 36 hours and $75,000 to put their ideas to the test in a pop-up restaurant.

“Inside the Walking Dead” (AMC at 10) peeks behind the scenes to give die-hard fans a look at the many layers that go into bringing the beloved zombie series together.

Recently renewed “The Night Shift” (NBC at 10) finds Krista helping a girl whose parents refuse to believe she has an eating disorder.

Halle Berry of “Extant” and Chris Colfer of “Glee” fame come to “The Tonight Show Starring Jimmy Fallon” (NBC at 11:35), along with music from Florida Georgia Line.

Comedian extraordinaire Joan Rivers is on the “Late Show With David Letterman” (CBS at 11:35), with a musical performance from Capital Cities.

Tony Parker from the San Antonio Spurs and actor Eric Bana stop by “Jimmy Kimmel Live” (ABC at 11:35) in this repeat episode. Plus, a performance from Linkin Park.

Rachel Lubitz