1) “Nature,” 8 p.m., PBS. Her name is “Grizzly 399” and her following is huge. She’s “the most famous bear that ever lived,” we’re told, using humans in the Grand Tetons National Park to shield her cubs from predatora. At about 24, she had quadruplets, which are rare; at 27 (a year past the average life span), she had her 23rd cub. It’s a remarkable story, often told through Tom Magnesen, the ace photographer who took this photo.
2) “Chicago Fire,” 9 p.m., NBC. For “Fire,” this is a change-of-pace – a single, life-and-death plot that takes up most of the episode. We won’t ruin any surprises, except to say that the heist is a huge one. Soon, one lieutenant (Sevaride) is missing and the other (his wife) is gathering forces. The result is sometimes compelling.
3) “Reginald the Vampire” season-opener, 10 p.m., Syfy. After the brutal “Chucky,” Syfy redeems itself with this genial show. Reg (Jacob Batalon) is a slushy-store clerk who became a vampire. The good news: His friend (Mandela Van Peebles, son of Mario) could be the local vampire king. The bad: Being a vampire, Reginald and his co-workers have found, “is a relationship obstacle.”
4) “The Masked Singer,” 8 p.m., Fox. Last week ousted Beets, a two-guy costume with a neat twist: Ruben Studdard, the second “American Idol” champion, was paired with Clay Aiken, his runner-up. Now four singers remain; they’ll open with “Praising You,” which was a hit for Rita Ora, who’s now one of the judges.
5) Comedies. On “Abbott Elementary,” Barbara invites Gregory to her Mother’s Day party. That’s 9 p.m. on ABC; then “The Conners” (in its 9:30 timeslot, to make room for “Jepopardy” at 8) has a crisis at the hardware store. On Fox, Frank wraps his investigation on “Animal Control” (9); then “Family Guy” sees an anniversary go bad.