Police Officer Jack Thornton was a member of the Royal Northwest Mounted Police (RNWMP) and a partner responsible and honoured by Elizabeth Thatcher.
His father, Thomas Thornton, was a Mountie who was killed in the line of duty. His younger brother, Tom, is a troublemaker, and at one point pursued a relationship with Julie Thatcher, Elizabeth's sister. His mother is still alive and still in his life, though not as much as she hopes. Despite having big plans in Cape Fullerton, Jack was reassigned to Coal Valley (later renamed Hope Valley) a little while after an accident at the mine at the request of William Thatcher, Elizabeth's father.
Originally he sent a demand to his superiors to leave, but eventually, Coal (Hope) Valley grew on him.
He was very helpful in season 5 episodes 1 and 2.
The beginning of Season 1, we saw the arrival of Jack Thornton coincide with Elizabeth's first week at Coal Valley.
Upon his first meeting of Elizabeth, he was interested in her. After meeting, he figured out that Elizabeth's father had sent him to protect and watch over her. Since he has given up an opportunity that he had hoped for to instead 'babysit' Elizabeth, he is upset that she had been the cause of his new mission. Over time, though, after getting to know her better, he grows to like and then falls in love with her.
However, the arrival of actress Rosemary LeVeaux reveals that Jack was briefly engaged before moving to Coal (Hope) Valley. This revelation causes a strain on Jack and Elizabeth's relationship. Jack tries to convince Rosemary he has moved on and despite her advances, she eventually comes to realise that they have both changed and they cannot have the same relationship as they once did. Jack finds out that Elizabeth may be leaving, and in his last effort to convince her to stay, he takes her on a walk, gives her a framed picture of them that he himself had sketched, and asks her not to leave. He tells her she's the "only one", to which she replies that she's "not going anywhere" and they share a kiss.
Throughout season 2, Elizabeth and Jack share a hot-and-cold relationship made complicated by family matters and former beaus. At the end of season 2, after they are trapped in the mine during a storm, they have a long-overdue heart-to-heart and they admit their love for each other and share another kiss. Later, Jack prepares to propose; however, Charles beats him to it. Charles is turned down by Elizabeth and the season 2/3 holiday special sees Elizabeth and Jack mending their relationship once and for all.
In season 3, Jack begins the new year knowing that Elizabeth only has eyes for him and that her relationship with Charles is over for good. Jack's mother shows up unexpectedly and meets Elizabeth and is suspicious of her, but through staying she sees Elizabeth for who she really is: a genuine, good person.
Halfway through season 4, Jack goes off on assignment to the notorious Northern Territories after his friend is killed in action in Jack's place. Prior to leaving, he proposes to Elizabeth and she eagerly accepts. At some point he writes a letter to Elizabeth in case he doesn't make it home - in it, he explains to her that he will be with her always and hopes she can find love again. He gives the letter to Abigail for safekeeping. He briefly returns during the season 4/5 holiday special, much to Elizabeth's delight, but has to leave soon after.
Early in season 5, Elizabeth is in the mercantile, where Florence rushes in. She ushers her outside to find an army of mounties walking through the town, coming home from the Northern territories. Elizabeth runs to look for Jack and when they finally reunite, they waste no time in getting married. A few days after their wedding, Jack is again sent away on assignment, but Elizabeth joins him on the trip there in place of their honeymoon. He is killed while away on a training mission. After his death, it's revealed that Elizabeth is pregnant and gives birth to a baby boy, whom she names Jack Thornton Jr.
Post-Season 5 Appearance
During the Christmas episode of When Hope Calls, the late Jack Thornton makes a reappearance to Abigail Stanton in which he asks her to send Elizabeth a message: “Will you let her know that I am happy that she is moving on with her life? And let her know that she is doing a fine job with little Jack, and I cannot be more proud of both of them.” He then turns away and vanishes and Abigail wakes up.
- Elizabeth Thornton (Wife): It was a lukewarm beginning to their friendship when he was first posted to Coal Valley. After a five-season long romance, Jack married Elizabeth in a beautiful wedding. After only a day or so of marriage, Jack got an assignment to train other Mounties, forcing him to leave his new bride. Tragically, a landslide occurred a few weeks into the training, and Jack pushed two of his men out of the way, sacrificing himself. His death was traumatizing and he left behind his young wife, Elizabeth, who was expecting the couple's first and only child.(Jack Thornton Jr.)
- Rosemary Coulter (Ex-fiancé): Prior to moving to Coal (Hope) Valley, Jack was in a relationship with actress Rosemary LeVeaux. At some point Jack had proposed to Rosemary, to which she had accepted but later broke off, which hurt Jack deeply. At the end of season 1, Rosemary arrives in Coal (Hope) Valley, in search of her 'fiancé' Jack, much to the shock and dismay of Elizabeth Thatcher. Rosemary tries to win Jack over in numerous ways, trying to get back to how they used to be, but he insists he has moved on. Rosemary eventually grows to realize that a romantic relationship isn't going to happen and instead turns her attention elsewhere. Despite their history, she and Jack remained firm friends.
- Leland Coulter: Lumber tycoon who is also a good friend to Jack Thornton upon his arrival to Hope Valley.
- Bill Avery: Someone whom Jack admires and looks up to. Bill later states that Jack was like a son to him.
- Abigail Stanton: Someone who acts as a confidante to Jack during his courtship with Elizabeth.
- In Season 2, he had planned to propose to Elizabeth at the schoolhouse. However, upon seeing Charles attempt to propose before him, he decided against it.
- He has surprising skill in painting and drawing.
- Jack is given a choice between Rosemary's New York glamour chicken fried steak and Elizabeth's crumby old burnt chicken fried steak. He satisfies his tum by eating both, but realizes that was a mistake when he gets to Elizabeth's.
- In Season 4, Before Jack left for the Northern Territories he proposes to Elizabeth and she eagerly accepts.