Endeavour left Lonsdale College at Oxford University late in his third year without taking a degree as a result of breaking up with a woman from Jericho named Susan.
Thursday names Endeavour his designated "bag man" and shows him the ropes as Morse begins to solve a string of complex murders, much to the envy and annoyance of some of his superiors, particularly Detective Sergeant Peter Jakes and Police Chief Superintendent Reginald Bright.
Upon returning to Cowley Station in 1966, Morse is received warmly by Chief Superintendent Bright and Sergeant Jakes, as Inspector Thursday begins to keep a more watchful eye on the young Endeavour.
As a result of the shooting, Morse begins to suffer from delayed stress and paranoia, as well as an increase in alcohol consumption at local pubs and in his own city flat.
After investigating several cases leading to the pillars of Oxford society, the finale of Series 2 ends with Thursday's being shot by ACC Deare, who is in fact the head of the corruption, who succeeds in framing Endeavour for his murder of the Chief Constable and the bilking of evidence.
Having averted a disaster at a nuclear power plant along with Thursday, Morse is awarded the George Medal and promoted detective sergeant in the series finale.
Thursday served in the North African and Italian Campaigns during the war as a soldier in the British Expeditionary Force after becoming a policeman in London in December 1938.
In the first series, Thursday names Morse his designated "bag man", much to the chagrin of DS Jakes and to the annoyance of the very procedural CS Bright.
Only staying a short time, Jakes was one of many boys who were the victims of sexual and physical assault by the "guv" of Blenheim Vale (now Alderman Wintergreen), a young Oxfordshire police officer (now Assistant Chief Constable Deare), and several other adult men in charge of the home.
When the chips are down, his loyalty to his troops – for all his bark and bite – is total.Bright is somewhat oblivious and is considered to be an "old school" police officer, very worried about appearances and courtesies when dealing with rank, royalty or the Oxford elite, and at first, like Sgt.
Bright suggests to Thursday that it is bad practice to enlist a DC as his bagman, but soon comes to better appreciate young Endeavour by the second series, after he returns from being shot and solving several complex cases.
As the series progresses, he slowly becomes a more sympathetic character; he is exceedingly protective of WPC Trewlove, for whom he has a soft spot and shows immense bravery when the situation calls for it, challenging the initial image of his being weak-willed and sycophantic.
His quiet courage and clear dedication to justice gradually helps to ease his and Morse's relationship onto a friendlier footing, with the two men slowly becoming respected colleagues and equals.
As a PC, he partakes in a great deal of legwork on the streets and is shown to keep his head in a crisis, taking command of a situation quickly and efficiently.
At the beginning of series 3, Strange is promoted to sergeant, and in the third episode he moves from uniform to CID, replacing DS Jakes as Morse's immediate superior.
Chief Superintendent Bright sees her as an attractive addition to the station and proves to be exceedingly protective of her; for her part, she becomes extremely fond of him in turn.
In a similar manner to Joan Thursday, Shirley Trewlove develops a distant yet romantic fondness for Morse which he also fails to openly reciprocate.
In the Series 3 finale, the bank where Joan works is robbed and she is taken hostage, along with the other employees and Morse, who comforts her during the saga and supports her through it, the two of them glad of each other's company during the ordeal.
She is a devoted wife and mother and in the early episodes acts in a friendly, maternal fashion towards Morse, welcoming him into the home and helping to provide care when he is badly injured.
As the wife of a detective-inspector, she patiently puts up with Thursday having to depart to solve a crime and sends her husband off in the morning with sandwiches and the daily command to 'Come home safe.'
Disgusted by her husband's behaviour, Win becomes more distant than ever, to the point where she asks for a divorce; however, they reconcile by the series' end after Fred stands up to the corruption alongside Morse, Bright and Strange.
He originally has a job in Oxford but is preparing to serve in the British Army, a role which he departs for at the end of Series 3, a change which Win finds difficult to adapt to.
Army life has been shown to have had an impact on Sam; he becomes a more mature, rounded character and takes his position as a Corporal seriously, rebuking himself when he believes he has failed in his duty.
He shows a respectful attitude towards his superiors as well as those in his military care, demonstrating loyalty to his army mates and arguing with his father over the arrest of someone whom he believes to be innocent.
Despite his chosen profession, and his seemingly detached nature, DeBryn is quickly revealed to have a softer side: he is shaken by the murder of a child in the Series 2 episode 'Nocturne' and confides his anger to Morse, entreating him to find the person responsible and showing how he has come to put his faith in the detective.
As a doctor, his upholding of the Hippocratic Oath means that he is willing to approach a dangerous situation to offer help to those in need; in Series 5 Episode 5, Quartet he is able to save the life of a young boy hit by a stray bullet although he is modest about accepting praise in the aftermath.
He remains loyal to Morse, Bright and Strange during the drastic changes at Castle Gate during Series 6, offering the three of them both personal and professional support while making his displeasure at the behaviour of Box and Jago known.
Having spent time reporting in Korea, she seeks to write the truth in her newspaper and her enquiries can occasionally place her in the line of danger, although she proves herself to be unintimidated and refuses to back down from a difficult situation.
She is one of the few who truly understands Morse's difficult temperament, on both a personal and professional level and recognises his need to successfully conclude a case, even when there are challenges involved.
A competent and dedicated nurse, she becomes the young Endeavour's love interest in the second series after caring for him when he suffered a concussion and inspiring and motivating him to finish a complicated case.