context: The story is set in early 18th Century Scotland. A group of Scots highlanders are tracking another clan who have stolen cattle from a lord. The protection of the lord's property, including his livestock, is managed by Robert Roy MacGregor, the man leading the trackers. One of his men, Alan McDonald, tells Rob and the rest of the party that they are about a day behind the thieves.The search party finally spots the thieves, camped out in a valley. Knowing that an attack at night would be unwise, Rob orders his party to get some sleep. He also says that he'll personally approach the thieves in the morning and try to negotiate with them. When Alan asks Rob why he thinks speaking to them will accomplish anything, Rob tells him "I know one of them."The next morning, Rob makes good on his word and wakes up the thieves in their camp. He tells them that the cattle belong to his lord and they'll all live if they lay down their weapons and surrender the animals. To prove his point, Rob tells his men to reveal their positions, which surround the camp. Their leader, Sibbald, mocks Rob's authority. When he tries to kill Rob, he is killed himself. Rob allows the rest of Sibbald's party to live and they leave. Rob returns home to his proud wife, Mary, and his two young boys. He spends a few days at home and he and Mary make passionate love under a tree.Rob Roy's village is under the protection of John Campbell, Duke of Argyll. While watching his best duelist, Guthrie, in a sword match, one of Campbell's vassals the Marquis of Montrose, meets with him. Montrose is accompanied by a foppish young man, Archibold Cunningham. Archie had been sent to Scotland by his mother, who had grown irritated by his promiscuous playboy behavior. Archie challenges Guthrie to a duel and Duke Campbell and his vassal Montrose wager heavily on the outcome. Campbell is surprised when Archie easily bests Guthrie, and Montrose wins a hefty sum.Rob meanwhile devises a plan to make money droving cattle: he decides he will ask Campbell to loan him 1000 guineas that he will use to buy cattle at a nearby port. He will raise the cattle and sell them back to Campbell at a profit. Campbell tells Rob to to draw up a loan agreement with Montrose. Montrose's chief banker, Killearn, is a treacherous businessman who is secretly loyal to Archie, whom Killearn believes is more ambitious than Duke Montrose. Killearn reveals to Archie that Rob will be receiving the 1000 guineas as coin and that Archie should prepare to steal it.The next day, Rob meets directly with Killearn and signs the papers to receive the credit. Rob leaves, charging his man MacDonald with collecting the credit slip. Killearn deliberately makes MacDonald wait all day while he deals with all his other clients. When Killearn finally calls MacDonald in to receive the loan, Killearn tells him that he cannot give him a credit slip and MacDonald must take coins instead, violating the agreement with Rob. MacDonald is reluctant but finally accepts the coin. On his way to deliver the money to Rob, he is pursued through the woods by Archie, who has prepared an ambush. MacDonald's horse carry's him into a rope strung across the path, and he is injured and thrown from his horse. He staggers away, hiding the money in a tree. Archie finds him and kills him, taking the money.When MacDonald doesn't show up, Rob goes back to Killearn, demanding to know what happened. Killearn tells him that he'd given MacDonald the money and he left. Killearn also suggests that MacDonald had stolen the money for himself and may have boarded a ship to America. MacDonald had earlier told Rob he wished to leave Scotland for Virginia. Rob refuses to believe that MacDonald would betray him and decides to take his case directly to Montrose. When he meets with the lord, he tries to strike a new deal for more money. Montrose will agree, provided Rob falsely testifies that Campbell is a Jacobite. Rob refuses, only knowing Campbell by reputation. When he suggests that Montrose is crooked, Montrose orders Archie to arrest Rob. Rob pulls a hidden knife and holds Archie at bay, pushing him over and running off. Montrose instructs Archie to find Rob and bring him to justice, "broken, but not dead." Archie sets out with Killearn and a small unit of soldiers.Rob returns home and tells Mary that he'll be leaving their home until he can figure out a plan to clear his name. Mary is angry, saying he'll be hiding like an animal. Rob leaves his younger brother Alasdair and a couple of other men loyal to him to guard Mary and the farm. Very soon, Archie, Killearn and the unit of soldiers sail across the lake in front of the MacGregor home and arrive early one morning. Mary gathers her boys and tells them to hide in the hills behind the house. She goes out to meet the landing party, frightened but confident. She defiantly calls Archie a fool when he demands to know where her husband is. Archie orders the soldiers to burn her house and kill the livestock. Killearn suggests that Mary step aside, but Archie grabs her hair and drags her into the house. He forces her over a table and brutally and gleefully rapes her. Her house burning around her, Mary finally walks out, shaken but proud. The noblemen and their soldiers depart on their boat as Alasdair arrives, yelling for the marauders to return and fight. They fire a warning shot at him and bleat like sheep as they sail back across the lake. Mary furiously washes her groin in the lake, and Alasdair realizes that she's been raped. Mary compells him to promise not to tell Rob, because she doesn't want him to get killed in his desire to avenger her honor. Alasdair reluctantly promises Mary he won't say anything.Mary formulates a plan of her own to prove Rob's innocence and honor. She discovers that Archie's lover, Betty, one of Montrose's servants, is pregnant with Archie's child. Spurned by Archie, Betty agrees to testify that she overheard Archie and Killearn conspiring to steal the money given to MacDonald. Mary comforts her when she admits that she's pregnant and becomes upset, saying she still loves Archie despite his evil nature. Mary tells Rob about Killearn's and Archie's dealings and Rob vows to bring them both to justice. Rob finds Killearn in a tavern. Guthrie attempts to defined him, and Rob kills him. When Rob arrives at a secret location with Killearn, he sends Alasdair to retrieve Betty, but when Mary goes to find her, she finds that Betty has hanged herself and is dead.Mary demands to meet with Killearn privately, demanding that he testify to restore Rob's honor. Killearn refuses, gaining the upper hand when he mentions that he remembers how Archie raped her and that the child Mary is now pregnant with may be Archie's and not Rob's. Enraged, Mary stabs him in the neck, bringing Rob and Alasdair. Rob tries to calm Mary down, leaving Killearn to Alasdair. Alasdair drowns Killearn in the lake. Rob and Mary's plan is foiled and Rob tells his brother to drop the body in the middle of the lake since Montrose will search for him.Alasdair joins Rob in the Highlands. They observe Archie's war party from a distance burning the house Rob & Mary had occupied after their own home was destroyed. Rob orders a retreat before Archie notices them; his own men are out-armed and outnumbered. Alasdair, angry over Archie's violation of Mary, takes a potshot at Archie, missing and killing one man. Archie orders his men to chase Rob's party into the mist covering the peaks. As he runs to catch up with Rob, Alasdair is shot, paralyzing his legs. Rob grabs him and carries him into the mist. As he dies from his wound, Alasdair tells Rob that Mary was raped by Archie.A soldier finds them and finishes Alasdair off. Rob overpowers the man and mounts his horse to escape, but it's shot out from under him and lands on his leg, trapping him. He's captured by Archie, who binds his hands and drags him behind his horse. At night, Rob is tied to a tree. He tells Archie that he a thief and rapist, and Archie tells him that Campbell's wife Mary was more enjoyable when raped than others who were willing, and that "not all of her objected." Rob lunges forward and bites at Archie ripping his coat. Archie beats him and has him gagged for the rest of the march home.When they reach the Bridge at Glen Orchy, Montrose is waiting. Rob is allowed to speak in his defense. He claims that Archie killed MacDonald and stole the money. Archie denies the charges and Montrose orders his men to hang Rob from the bridge. Rob quickly grabs the rope binding his hands, loops it around Archie's neck and jumps from the bridge. The rope pulls Archie to the edge where one of the soldiers uses a sword to cut it, freeing Rob, who plunges into the stream below - Archie is still alive. Rob washes downstream with the current, going over a small waterfall. On the bank, he finds the rotting carcass of a dead ox and quickly guts it, using the animal to hide from the search party, who won't approach because of the stench.Rob rejoins Mary at a safe house,. which Mary had earlier negotiated from Campbell himself and secured the property under his protection. Rob confronts Mary about the rape but realizes she still loves him and that the child she bears is definitely his. Rob recovers from his wounds and visits with Campbell, seeking a way to settle his dispute with Archie. Knowing Archie's skill with a sword, Campbell reluctantly agrees to sponsor Rob in a fair duel. He tells Rob that as a prudent man he ought to bet on Archie. Rob tells him to bet any way he chooses. Rob bids his family farewell, telling his sons to ask their mother about the new addition to their family. Mary asks Rob what to name their child if Rob doesn't return: he tells her to name it for himself if it's a boy and for herself if it's a girl.On the way to Montrose's court. Rob convinces Campbell to pay Mary's and his children's living expenses if he loses the match with Archie. They agree on a high sum and Campbell exclaims that he likes Rob's negotiating style.Rob arrives at Montrose's court where he and Archie will duel to the death with swords. Campbell and Montrose agree on a wager. After laying out the customary rules about backstabbing and quarter, "no quarter being given or asked." The two duel, and Archie has obviously superior skills to Campbell. He toys with Rob, slashing him superficially several times on his torso, and then on his dueling arm, disarming him.He lifts Rob's chin with his blade, and receives a nod from the moderator to end the duel and Campbell's life. Rob suddenly grasps Archie's sword blade at his own neck with his bare hand. He picks up his own sword from the floor next to him, and Archie is too surprised for a moment at Rob's sudden action to do anything. Rob swiftly cuts Campbell deeply from his shoulder to his sternum, opening a wide wound. Archie is shocked, gasps, blood spilling from his mouth, stumbles, and falls dead.Rob settles his wagers with Campbell and Montrose and leaves. Montrose tells Archie's sponsor that he will hold him to their wager, meaning that all of Campbell's debts are wiped clean. Rob returns home to Mary who is overjoyed to see him.
question: Who stabs Killearn in the neck?
answer: Mary