R.I.P. Hercule Poirot

Agatha Christie’s Belgian detective Hercule Poirot (David Suchet) returns to “Masterpiece Mystery!” with his waxed mustache, three-piece suit and formal manner — so formal that he even refers to himself in the third person (Sunday, 8 p.m., PBS). Poirot cuts an odd figure, but he’s so good at piecing together clues that the provincial British police officers who accompany him to crime scenes can only mutter, “Blimey!”

In “The Big Four,” Poirot sticks his nose into international espionage in the run-up to World War II, investigating the suspicious death of a Russian chess master. Is it the work of the Big Four, a shadowy group with the charming habit of sending polite note cards to its victims? “What eez zees Big Four?” Poirot asks in his stagy accent.

Whatever eet eez, three bodies pile up in the first 30 minutes — actually four if you count Poirot, who is buried in the opening scene.

“Ray Donovan”

Sunday, 8 p.m. (Showtime)

Last year I knocked this dramatic series for rubbing our noses in sick sexual encounters and bloody corpses. I found Liev Schreiber too gloomy as a fixer for the rich and famous — a thug who solves their problems with muscle and manipulation, but not much entertainment value.

Well, either the series got more interesting or my life got more depressing, because season two strikes me as a pretty good time. Schreiber has found intriguing nuances in his character, and the supporting cast of scoundrels (Jon Voigt, Elliott Gould) runs the gamut of masculinity from asinine to atrocious. The series is still gloomy, to be sure, but there’s just enough tough-guy poetry to take the edge off.

“Masters of Sex”

Sunday, 9 p.m. (Showtime)

Everybody but me loves Showtime’s fictionalized portrait of 1950s sex researchers William Masters (Michael Sheen) and Virginia Johnson (Lizzie Caplan), so I thought I’d give it another try in season two. The credit sequence certainly promises sexy fun and intellectual substance, but in my opinion, this week’s episode fails to deliver.

After he delivers a baby with “ambiguous genitalia,” Masters holes up with Johnson in a hotel room, using assumed names to hide their affair. A boxing match plays on the room’s TV throughout the entire episode — a pretext for the couple to discuss the connection between ambiguous genitalia and 1950s notions of masculinity. Sheen has precisely one facial expression — constipated — while Caplan is so focused on precise articulation that her character never comes to life.

Their conversation, which is supposed to carry you through the hour, is depressive and depressing. They try role-playing a married couple, but even they realize they can’t get any sparks going. Johnson admits, “I guess neither one of us has a particularly interesting story, do we?” She said it, not me. CV

Dean Robbins is a syndicated TV columnist from Madison, Wis. He graduated from Grinnell College and went on to become an award-winning journalist, but he’s been a committed couch potato long before he figured out a way to get paid for watching TV. See more of his work at www.thedailypage.com.