Not to get all melodramatic or anything, but Grantchester opens Season 4 with life-threatening major surgery. 

The popular 1950s PBS drama, which resumes Sunday at 9 p.m. ET (check local listings), faces the unhappy task of slicing the show open and cutting out its main character, James Norton's (below left) Sidney Chambers. 

As so often happens with operations like this, we may not know for weeks whether it was a success. The producers are exuding optimism, for what it's worth, having already renewed Grantchester for a Season 5.  

There are times this Sunday when, frankly, it feels a little rushed and dramatically compacted. That doesn't necessarily mean the patient won't recover.

As PBS has previously announced, the show is really undergoing a full vicar transplant, inserting Will Davenport (Tom Brittney, top) in place of Sidney. 

Sunday's premiere, which runs the first two of the season's six episodes back-to-back, doesn't give us a real sense of Will. All we really learn is that he's a former inner-city chaplain with a social conscience and that the social conscience part seems not to be incidental.

To a much greater extent than in the previous seasons, the developing social justice movements of the 1950s – many centered in America, but with ripples felt in countries like Britain as well – immediately begin feeling more prominent. 

As with PBS's sister 1950s British drama Call the Midwife, the wider world seems to be generally seeping more prominently here into a drama that in many ways felt isolated. 

Where Sidney has always loved to sit around listening to jazz while he's drinking, this season opens with Little Richard ripping his way through "Long Tall Sally." Later in the episode, we get a prominent dose of the 1954 hit "Earth Angel," in a version that sounds more like Britain's Southlanders than America's Penguins. 

All this gives Grantchester a different feeling and rhythm, though it's still going to be a police procedural with Detective Inspector Geordie Keating (Robson Green) spearheading investigations into a weekly crime. With a whole new team, though, including a new stationhouse colleague in the pragmatic Detective Constable Larry Peters (Bradley Hall), the stories could branch out a bit.  

Most importantly, with no disrespect to social justice, Grantchester must quickly establish a relationship between Geordie and Will that's as strong and satisfying as the one Geordie has had with Sidney. 

This is a buddy show. No buddies, no show. 

Sidney's final hours feel like his previous three seasons on steroids, as he gets whipsawed between hope and despair. He responds by drinking heavily and realizing after he sobers up that the bottle let him down. Didn't solve anything. 

Without dropping any spoilers, the specific circumstances of his impending departure could constitute either an awakening or a Hail Mary. 

In either case, Sidney has had a good run, give or take feeling tormented all the time.     

A small-town vicar with a taste for jazz, a weakness for alcohol and a serious case of self-doubt, Sidney gradually became Geordie's volunteer sidekick. What started as an accident became a near-obsession. 

Every week Sidney and Geordie teamed up to tackle one of the extraordinarily high number of murders that seem to occur in their peaceful little English village. 

We also watched Sidney agonize his way through an on-and-off relationship with his true love, Amanda (Morven Christie) – a relationship whose ending bordered on flat-out cruel. 

Simultaneously, straight-arrow Geordie was having a crisis with his loyal wife Cathy (Kacey Ainsworth). The marriage felt very tenuously patched back together toward the end of last season. 

In fact, the murders sometimes seemed almost incidental last season, as Cupid also found Sidney's scowling housekeeper Sylvia (Tessa Peake-Jones) and Sidney's fellow man of the cloth, curate Leonard Finch (Al Weaver).

Leonard's canoodling had a particularly dangerous edge, since the slightest public sign of gay affection in 1950s Britain – or most of the world – could send you to prison.

But with social justice apparently a featured item on the menu this season, Leonard may be right in step.