Robson Green and Tom Brittney star in "Grantchester"

Recently, investigative journalist Billy Jensen popularized the term "citizen detective," which he describes as an individual who devotes their time and expertise to helping authorities solve crimes, without compensation or expectation of reward. Thanks in large part to technological advancements and sites like Reddit, amateur sleuths have been able to funnel their passion for true crime into solving unresolved crimes from all around the world.

While this kind of detective work is relatively new in the real world, we have seen numerous amateur detectives on the small screen over the years. For instance, Jessica Fletcher helped solve countless crimes in "Murder, She Wrote," and the Scooby gang has brought down an endless supply of villains in "Scooby-Doo." On Sunday, July 14, "Grantchester" returns to PBS for its fourth season, and its citizen detectives continue their quest for truth.

Based on the successful 1950s-set The Grantchester Mysteries book series by James Runcie, the period drama follows the adventures of a charismatic Anglican vicar and former World War II Scots Guards officer Sidney Chambers (James Norton, "McMafia") as he develops a penchant for sleuthing. After receiving a visit from a deceased man's mistress who believes his death was not a suicide but a murder, Sidney is implored to investigate the man's demise, and finds he has a knack for it.

Chambers' sleuthing puts him on a collision course with the grumpy, overworked fellow war veteran Det. Insp. Geordie Keating (Robson Green, "Strike Back"), who does not approve of the vicar's questioning of witnesses and suspects. However, the methodical copper reluctantly comes around, and the unlikely pair sets out to investigate a variety of local crimes.

Like all good fictional partnerships, the duo does not always see eye to eye, and their investigative methods and personal lives differ greatly from one another. Yet, with all the differences that separate these men, they somehow manage to look beyond them and focus on what is important: helping others.

The new season of this adaptation marks the beginning of a new chapter with the introduction of Rev. Will Davenport (Tom Brittney, "Outlander"), a former inner-city chaplain and man of the people who embodies the changing post-war world. The hip reverend rides a motorcycle and listens to rock 'n' roll. He is young and does not possess the post-war emotional baggage that many others, including Sidney, struggle with. Much like his fellow man of the cloth, he is considered a "boat-rocker" who embraces the future.

The young new vicar is caring, confident and self-assured, and he strives for social justice. According to ITV, the original broadcasters of the drama, Will is a man of God but has a bit of the devil inside of him. This dichotomy, as well as his troubled past, is explored over the course of the new season.

Tom Brittney in "Grantchester"

How will the skeptical DI Keating draw him into his world of crime-solving? Only time will tell, but what is certain is that the return of "Grantchester" marks the end of era as fan favorite Norton moves on to other projects after this season.

In a PBS news release, "Masterpiece" executive producer Rebecca Eaton said, "It's a bittersweet time for 'Grantchester' fans, who will be cheering the return of the series but crushed to say goodbye to James." She continued by adding that his last episodes are brilliant, and that the audience will be captivated by an interesting new vicar.

This feeling was echoed by executive producer Diederick Santer, who said: "While I'm sad that these will be James Norton's final episodes, we will make sure he goes out with a bang. We've got exciting plans for where the show is heading and the vicarage won't be vacant for long."

Last time we visited "Grantchester," Norton's Sidney Chambers wrote his letter of resignation after losing faith in the church, and he planned to move to London with Amanda (Morven Christie, "The Bay"). Believing that his community needed him now more than ever, he ultimately broke Amanda's heart and decided to stay put. Will the crime-fighting vicar find love again or forever stay adrift?

Sunday evening has always been important in the history of television. Even when the medium was still in its infancy, the night boasted legendary series such as "Alfred Hitchcock Presents" and "The Ed Sullivan Show." For decades following these two classics, the night was dominated by Disney specials, but the tide started to change in the 1990s and truly changed in 1999 with the debut of "The Sopranos" on HBO. 

Since then, Sunday nights have been the time-slot for prestige dramas. From AMC's "Mad Men" and "Breaking Bad" to Showtime's "Homeland" and HBO's "Game of Thrones," a bevy of award-winning dramas have claimed Sunday as their home, ensuring they would be on the tip of everyone's tongue throughout the week. Along with the above, PBS's "Masterpiece" has consistently delivered smash hits such as "Sherlock," "Downton Abbey" and now "Grantchester."

After a two-year absence, "Grantchester" returns to PBS on Sunday, July 14, for Norton's final season. In the wake of the much-discussed third season, a lot has happened in the Cambridgeshire village. Now it's 1956, and change is in the air. There is a new vicar in town and he is shaking things up with his progressive ideas. Will the changing times leave DI Keating behind? Tune in to the season premiere to find out.