“A man only gets one father,” Fred Thursday told Morse in Endeavour series one, when the young officer was demurring about returning home to attend his dad’s deathbed. Of Thursday’s many sayings, this one proves the least true in Endeavour’s case. Morse had one father, yes – a strained relationship with an estranged man whose dying words to his constable son were that he’d never liked the police – but in Fred Thursday, he also had another. Has another, that should say, as Thursday is still very much part of Morse’s life. It’s a hard-to-ignore fact though, that a separation between the two is inevitable and fast-approaching. Roger Allam’s DCI was invented solely for the Inspector Morse prequel and is therefore absent from Morse’s later years. Endeavour creator Russell Lewis built Thursday and Morse’s relationship in the knowledge that eventually, he would have to tear it apart. Whether in this series or the next, something is going to happen to make Morse never again mention the name Fred Thursday. The question is: what? The seeds of a conflict between the erstwhile mentor and his brilliant young student had already sprouted in series seven, which saw Morse and Thursday at loggerheads investigating the case of the Towpath Killer. Morse criticised and undermined Thursday’s police work, and Thursday angrily reminded the erudite youngster that not every case is a crossword puzzle that can be solved using anagrams, opera, or the periodic table. Their animosity led to an embarrassing stand-up fight over the corpse of a victim, and a falling out only becalmed after a letter of apology and a Venetian canal-side shoot-out. At one time, Morse and Thursday were a two-man team against the world. Driving the roads of Oxford, swapping theories and saving the day. Morse made solves Thursday never could have, and Thursday advocated for his unlikely bagman’s brilliance to Bright and others, having spotted the potential of Endeavour’s unusual mind right from the start. Much has happened since Thursday tenderly covered an injured Morse with an overcoat on the family sofa and let him sleep surrounded by the familial warmth of the Thursday home. No small amount of what’s happened is between Endeavour and Fred’s daughter Joan, or “Miss Thursday” as Morse affectionately calls her. They grew close after Endeavour’s daily trips to the Thursdays’ semi-detached to drive Fred to work, and shared a terrifying ordeal in series three finale ‘Coda’, when both were held at gunpoint during the raid on Joan’s bank. Theirs is less a will-they-won’t-they relationship than an if-they-will-they-won’t-for-long romance. Once again, a Damoclean sword hangs over the pair. Fans know that Inspector Morse remains a lifelong bachelor, so any love they share is doomed not to end in anything lasting. Series eight sees Joan, now a social worker caring for neglected children, accept a dinner dance invitation from Morse’s former flatmate and future superintendent Jim Strange. That supports a theory held by some fans that Joan is destined to become Mrs Strange, a character about whom we know nothing from the Inspector Morse TV series or original Colin Dexter novels. Seeing the ambitious woman of conviction he loves settle for a man as pedestrian as Jim Strange may well be enough to break Morse’s heart and put him off relationships for good. Judging by the cynical, heavy-drinker Endeavour becomes, in that case Miss Thursday would surely have made the right choice, though that’s a chicken-and-egg situation if ever there were one. One thing sure to drive an unmovable wedge between Morse and Fred Thursday would be if Morse were to mistreat Joan. Fred and Win love their daughter fiercely, and if Morse hurt her badly, it’s easy to imagine that no amount of affection or history between Morse and Fred would bridge that divide. Thus far, Morse has always been – to use Joan’s words – the perfect gentleman towards her. He covered for her when she snuck out to a club with DS Jakes, and warned Jakes to treat her well. When she left home, traumatised by the bank raid, and ended up living unhappily with a married man, it was Morse she wordlessly phoned for help. When that married man kicked her out, pregnant, it was Morse’s doorstep she showed up on. And when Morse saw the black eye her boyfriend had given her, it was him who could barely contain his rage, and then offered to marry her. Heartbreak is one possibility, grief is another. The terminus Endeavour is heading towards may not be Morse losing Joan to another man, but losing Joan altogether. Her social work role has already led to crossover with police investigations. Perhaps she becomes fatally entangled with a dangerous case, which is what causes Endeavour and Fred’s rift. After the murders of Constable Carter (whom Fred took under his wing in much the same way as he did Endeavour) and DC Fancy, we’ve seen how Thursday holds onto guilt. How might he react if Morse made a mistake on a case that lost him his daughter? The shame and pain would surely be enough for Morse to want to close a door on the Thursday family in his mind, while their grief could send Fred and Win away from Oxford and the memories it holds. Whatever causes the breach, when he loses Fred Thursday, Endeavour won’t just be losing a guvnor. When Fred asked Morse’s neighbour Monica to check in on him and call night or day if he needed him, he may have said he was just a colleague, but that’s not so. He’s family. To the end.