Far and Away

In Ireland in 1892, Joseph Donnelly's family home is burned down by his landlord Daniel Christie's men led by Stephen Chase because of unpaid rent. Vowing revenge, Joseph unsuccessfully attempts to kill Daniel. Joseph meets the landlord's daughter Shannon, who has rebelled against family tradition and made plans to claim free land in America. She offers to take Joseph with her as her servant so she, a single woman, can travel without scandal. Joseph agrees, convinced he can also stake a land claim.
On a ship bound for America, Shannon meets McGuire, who warns her that the free land is very far away in Oklahoma. She explains that her collection of valuable silver spoons will cover all expenses and he offers to help her find a shop to sell them to. On arriving in Boston, McGuire is shot and Shannon's spoons fall out of his clothing and get snatched up by passersby. Joseph rescues her but not the spoons. A worker for Ward Boss Mike Kelly, a leader of the Irish immigrant community, introduces them to him. Kelly finds them lodging and jobs, but only one room, which they must share. To avoid scandal, Joseph says she's his sister.
Joseph and Shannon become attracted to each other, but both keep up a front of indifference. One night Joseph rushes out to Boss Kelly's club, where a bare-knuckle boxing match is underway. Joseph challenges the winner, knocks him out and soon becomes a regular at the club. Back in Ireland, the Christies' house is burned down by angry tenants in the Irish Land War, so the Christies decide to emigrate to America, hoping also to find their daughter.
Joseph is told Shannon is at Kelly's club. Rushing to the club, he discovers Shannon on stage as a burlesque dancer. He tries to cover her with his jacket, demanding that she stop dancing. The Irish men surrounding the couple beg him to fight and offer him a small fortune ($200). Shannon, who previously scorned boxing, urges him to fight, since the money would get them to Oklahoma. Joseph agrees and is winning until he notices one of his backers (a member of the city council) groping Shannon on his lap. Joseph pushes through the crowd to free her, but is pushed back into the ring, where his foot accidentally "toes" the line, falsely signaling he is ready to begin fighting. But he isn't ready and the Italian lands a sucker punch, after which he's beaten.
In retaliation for the hundreds of dollars Joseph's boxing loss has cost Boss Kelly and his friends, Joseph is thrown out into the street outside the club and he meets a policeman who shows him a picture of Shannon asking if he's seen her. He then comes back to the room to find Kelly and his thugs searching their room for the money he and Shannon saved. With their valuables having been stolen by Kelly's thugs, they're both then thrown out into the streets. Joseph and Shannon are left homeless.
Cold and famished, the pair enter a seemingly abandoned luxurious house. Joseph encourages Shannon to pretend the house is hers and he is her servant, but she begs him to pretend they are married and the house is theirs. During that tender moment, the owners of the house return and chase them away, shooting Shannon in the back. Joseph brings Shannon to the Christies, newly arrived from Ireland. He decides Shannon will be better cared for by them and leaves despite his obvious feelings for her.
Joseph head west in Ozarks. Joseph finds work laying track on a railroad for the last few months, seemingly abandoning his dream of owning land. Told a wagon train he sees out the door of his boxcar is heading for the Oklahoma land rush, Joseph abandons the railroad and joins the wagon train, arriving in Oklahoma Territory just in time for the Land Run of 1893.
Joseph finds Shannon, Stephen, as well as the Christies already in Oklahoma. Stephen, having seen Joseph talking to Shannon, threatens him that he will kill him if he goes near Shannon again. Joseph buys a horse for the land rush but the horse dies in a few hours and he is forced to ride an unruly horse he manages to tame. On this horse, he quickly outpaces everybody and catches up with Shannon and Stephen, having discovered that Stephen cheated by illegally inspecting the territory before the race and is headed for extremely desirable land he found.
Joseph is ready to plant his claim flag. Shannon rushes to his side and rejects Stephen when he questions her actions. Joseph professes his love for Shannon. They drive their flag into the ground and claim the land together.

Question: What does "toeing" the line indicate?
Answer: It signals that one is ready to begin fighting.