When there are so many great Masterpiece mysteries available to watch – Grantchester, Prime Suspect, Unforgotten – it’s inevitable that something falls by the wayside. We’re here today to admit that for us, the show that we were skipping over was Masterpiece’s Endeavour.

We have discovered, dear reader, that that was a huge mistake.

If you’ve made the same mistake, it’s time to remedy that error. A prequel to the beloved Inspector Morse, the show follows the young detective as he makes his way through the ranks – and all the mysteries in Oxfordshire! With its impressive cinematography, moody score and swoon-worthy lead, Endeavour is everything that we’ve come to love and expect from Masterpiece. Each episode is rife with twists and turns, from the thrillers themselves to the dizzying social mores of England in the 60s.

Curious? You Should Be! Season Six of Endeavour premieres this Sunday at 9pm on WGBH 2 and streaming on WGBH Passport (learn more about WGBH Passport here). And if you’re like us and have missed the series thus far – or you just need a refresher for Sunday – here are the six essential Endeavour episodes to watch before season six!

Meet the Protagonist
Season 1, Episode 1: Girl – Season 1 and 2 available on Amazon Prime; Season 3 through 5 on WGBH Passport
With our first introduction to Endeavour Morse, Fred Thursday, and the cast of characters at Cowley Police Station, this is the perfect place to begin your endeavor into Endeavor. When a twisty little murder involving drug dealing, affairs, and epilepsy comes on Thursday’s docket, it’s the perfect showcase for the young Detective Constable Morse’s intricate mind for mysteries – and tendency to be perceived as a nuisance by those in charge.

Endeavour – Trewlove
MASTERPIECE Mystery! “Endeavour” Season 4 Part One: “Game” Sunday, August 20, 2017 at 9pm ET Endeavour, struggling with Joan Thursday’s sudden departure, finds himself consumed by a nightmarish hunt for a serial killer. He must race against time to find the connection between a chess-playing “thinking” machine and a baffling drowning. Shown: Dakota Blue Richards as WOC Shirley Trewlove. Photo courtesy of ITV Plc and MASTERPIECE. For editorial use only.

Getting The Team Together
Season 3, Episode 3: Prey
This episode is pretty fantastic overall – not only does beat cop Jim Strange become a regular when he is promoted to Detective Sergeant (which puts a bit of a bee in Morse’s bonnet), but the station begins to rely more heavily on Woman Police Constable** Trewlove, a smart and sassy young woman who keeps the rest of the team on their toes. Add in a delightful background story for Chief Superintendent Bright and an intense mystery that involves secret affairs, creepy taxidermists and tigers, and you have a great episode with a lot of development!
**her actual title, egad.

Adding in a Little Romance…
Season 3, Episode 4: Coda
This episode covers a lot of ground, kicking off professional and personal concerns that Morse carries with him into Season 6. When Morse sits his Sergeants exam, he soon finds out that Cowley Station isn’t big enough to maintain two Sergeants – a fact that causes the tension that’s been simmering between Morse and Strange to come to a head. As if the hostility between partners wasn’t enough, Morse and Miss Thursday are held hostage in a bank robbery, DI Thursday’s ailments come to a head, and Morse’s main love interest is introduced.

…And a LOT of Drama
Season 4, Episode 4: Harvest
Not only does this episode’s mystery pivot around a Nuclear Power Station, and some insane Wicker Man-style rituals– but it also gifts us with a wealth of personal drama. When DI Thursday finds his estranged daughter, his instant dislike for her boyfriend results in an encounter that has ugly repercussions for Joan… and Morse. But as the interpersonal turmoil mounts, so does their case. When a truly explosive end threatens, Morse and Thursday’s bravery results in a commendation from the Queen herself – and a promotion for Morse.

Endeavour – Morse and Thursday
Endeavour, Season 5 MASTERPIECE Mystery! Sundays, June 24–July 29, 2018 at 9pm ET on PBS Part One: "Muse" Sunday, June 24, 2018 at 9-10:30pm ET Past and present collide in Oxford, as the auction of a priceless Faberge Egg gets underway at Lonsdale College. It soon attracts the attention of an infamous international thief – and the police – when a failed burglary attempt is reported. However, they soon have a bigger case to solve, as a series of gruesome deaths have Morse and Thursday searching for a serial killer. Meanwhile, newly-promoted Endeavour struggles with his role as he's forced to mentor young detective constable George Fancy. Shown from left to right: Roger Allam as Fred Thursday and Shaun Evans as Endeavour Morse. For editorial use only. Coutresy of ITV and MASTERPIECE

Pull it All Together
Season 5, Episode 1: Muse
A Fabergé egg, working girls, and religious art history string together in a case that tests Morse’s mettle with mysteries… and with women. As if a frustrating investigation wasn’t enough, Morse’s new promotion brings new responsibilities – and he’s assigned a young constable who is almost the exact opposite of our high strung hero. George Fancy cares a little more about women and drink than the job, and his carefree attitude set Morse’s teeth on edge from the start. As if that wasn’t enough, Joan Thursday has shown up back in town…

And Get Ready For Season Six!
Season 5, Episode 6: Icarus
After Cowley announces its closure, due to a merger of city and county forces, Morse and Trewlove are sent on one last case: going undercover at a boys school to investigate the murder of a professor. Just as the team begins to drift apart, a shocking tragedy pulls them back together, setting up events and questions that we hope will be answered in season six. But the worst cliffhanger to us? What was Joan’s answer to Morse asking her on a date?!

And, just because we like you, here’s a little preview of the new Season. See you on Sunday!