He first appears in the episode, Kissed, when Greer goes to the kitchen looking for items for a picnic, assuming he can't read. She leaves the list after being called by Mary and he sends the basket to her that night.
After Greer's romantic night with Prince Tomás is ruined, she goes to the kitchen to return the food and ends up chatting with Leith. He reveals that he comes from a family of shepherds but chose to leave them to work in the palace. They share a brief kiss, Greer's first, and she leaves troubled. Later he's seen with a stain of white flour in his cheek, marking him as the man that Nostradamus prophesied that Greer will fall in love with.
In Hearts and Minds, Leith meets up with Greer at the Costume Ball after she leaves a costume for him in his room. When they see each other at the dance they eventually share a kiss.
In A Chill in the Air, Greer makes an attempt to spark things up with a visiting lord but is distracted by Leith and wine is spilled on her dress. In the halls, Leith meets up with her and offers to clean her dress. Later, Leith delivers the dress to Greer and when he starts flirting with her she reminds him how she needs to find a husband and asks him to not to flirt and talk to her. At the end of the episode, Leith assumes she's there to tell him to do something, she goes and kisses him, after she tells him that she will be married one day but doesn't want to regret what she could have done with her time at the castle.
InLeft Behind, Leith and Greer are spending time together by cooking in the kitchen. When the castle is under siege, Leith, Greer, and the other kitchen servants are trapped in the kitchen. During the feast, a guard tries to find out where Greer is and draws his sword against Leith.
In The Darkness, he and Greer discuss First Light and how he has to prepare lots for it. During the festival, he comes up to her with an invitation from Lord Castleroy to dine with her. During dinner Lord Castleroy gets caught on fire and Leith puts it out, after Greer shows affection towards Leith and asks him if he is burnt, Lord Castleroy appears to know that there is something going on. Later Greer convinces Lord Castleroy to let Leith have a position in one of his spice factories as a trainee because of saving his life.
In Monsters, Leith is first seen giving out cake to the female servants on whom will find the bean to become Queen of the Bean for a day. He seems to be jealous watching Mary bless Greer and Lord Julien's engagement. Later, Leith visits Greer’s chambers for one last stolen moment only to be caught with her by Lord Julian. Leith is taken to the dungeon and Lord Julian kindly breaks their engagement. As a result, Leith is drafted into the royal army instead of being sent to prison thanks to Lord Castleroy, Greer's fiancee.
Leith returns in Higher Ground. In battle, Leith saves Prince Francis from nearly being killed. Later, they are ambushed once again by the English. They have a huge canon making it impossible for them to escape. They have no choice but to stay and fight or to die trying. Francis notices that the English have stashed all of their gunpowder right beside the canon, and he comes up with an idea to take them down. The others, however, aren't too enthusiastic, claiming that they’re merely “chess pieces” in this war. Francis insists that he doesn't view them as throwaway pawns. He’s able to convince the men to carry out his plan. They distract the English while Francis climbs atop a hill and fires a single arrow into the stockpile of gunpowder. His aim is perfect and his the target. The men cheer at their success, but then they realize that Leith has been gravely injured. Francis refuses to leave him behind but Leith insists that it’s pointless. Francis asks Leith if there’s anything for him in France—or anyone, rather. He says that there is a girl he loves back at court, but he’s in no position to be with her. Francis begs to differ. Leith is a friend of the Dauphin now, so he may have more to offer his lady love when he gets back. Titles, land, money, and knighthood. Whatever awaits Leith, the prospect gives him the ability to summon his strength and carry on. Leith agrees to this and Francis helps him walk to safety.
Leith is back at the French Court in Slaughter of Innocence. Leith approaches Francis about the land deed he was given as reward for what happened on the battlefield. Francis regrets not being able to give him a title and wishes his new friend luck with the girl he wants to impress, just as a member of the king's guard harasses a young woman in the hallway. Leith steps in and gets him to back off, but he has to reject her offer to get a drink due to his loyalty to Greer and eagerness to show her what he has to his name. He goes to see Greer in her room and tells her of how he's now a noble and the land he received from Francis. However, whatever her feelings for Leith may be, Greer tells him that he's the comfortable choice - someone who can't cover even 1/10 of her father's debts, someone who wouldn't be able to keep her sisters from being sold to the highest bidder. Before leaving for the naval spectacle, he tells her to take a risk and to trust love, for once in her life.
During the spectacle, Greer believed Leith was on the ship that exploded and was proven wrong when he was shown to have survived the naval spectacle stunt. In her room, he believes that they are about to give themselves to each other, she cannot marry him. He takes the words harshly, tearing into her about how he'll rise to become the man she thinks she needs and how he's to never be hers again, before storming off and leaving her emotional.
By the end of the episode, Leith meets the woman from earlier, whose name turns out to be Yvette, and attempts to buy her a drink, though she rejects the offer, saying she has to go meet a man.