1.1 Edmund is hanging around the royal court with his father. Gloucester is embarrassed that he has an illegitimate son, so he makes awkward jokes about having sex with Edmund's improbably fertile mother while he introduces his son to his friend, Kent.
1.3 Edmund confesses to the audience that he's going to con his way into getting a lot of wealth and power. First, he fools his father into thinking his brother Edgar wants to kill him. Then he convinces his brother that he should hide out and not talk to their father.
2.1 Edmund convinces his brother to run away from home. Then he stages a fight with his brother and cuts himself so that it looks like he was trying to stop his brother from getting away. When Gloucester comes in, he's impressed by Edmund's devotion. He tells Edmund that he will inherit all the family's money and land instead of Edgar.
2.2 Edmund breaks up a fight between Kent, Lear's servant, and Oswald, Goneril's servant.
3.3 Gloucester tells Edmund that he is going to go outside to help Lear, who has been purposefully locked out of the castle. He asks Edmund to distract Cornwall, who is in charge of this half of the kingdom and who has made it clear that no one is supposed to help the King. Gloucester also tells Edmund that he has received a letter about an army coming to Britain to do battle with Cornwall. Edmund promptly decides to betray his father and tell Cornwall both of these things, because he's a villain and that's what he does.
3.5 Cornwall praises Edmund for telling him about his father's plans. As a reward, Cornwall tells Edmund that his father will be punished and that he, Edmund, will become the new Earl of Gloucester.
3.7 Cornwall tells Edmund to take Goneril back to her castle. It is clear that Cornwall does this because even he thinks it would be weird for him to capture and torture Gloucester while his son was present.
4.2 Edmund seduces Goneril, and by the time she arrives home, she's totally in love with him. She kisses Edmund good-bye and swears to send him a message soon.
5.1 The next time we see him, Edmund is seducing Regan, Goneril's sister, and swearing that he's never had anything to do with Goneril. Later, he brags to the audience about how much they both love him, discusses which one he should choose, and wonders if Goneril will kill her husband to be with him. What Edmund does know is if he manages to capture Lear and Cordelia, he'll make sure they don't survive to take over the kingdom. Edmund has decided that Britain is going to be his kingdom – and he won't allow any competition.
5.2 Edmund succeeds in capturing both Lear and Cordelia, and orders one of his soldiers to execute them. When Albany comes in and asks where Lear and Cordelia are, Edmund distracts him while he is praised by everyone else for leading them all to victory. When Regan and Goneril start fighting over him, Albany suddenly announces that Edmund is a traitor; he says he knows that Goneril and Edmund have been plotting his death. A guy in disguise shows up and challenges Edmund to a duel. The two men fight, and Edmund gets a sword in the stomach. The guy in disguise turns out to be Edgar, Edmund's brother. Edgar tells him their father is dead. Speaking of people dropping like flies, it turns out that Regan has also just died, poisoned by Goneril. Oh, and Goneril stabbed herself. Edmund is pleased that two women died out of love for him. As he is about to die it himself, Edmund confesses that he ordered Lear and Cordelia put to death. His confession saves Lear (for about five minutes), but comes too late to spare Cordelia's life. Edmund's demise passes almost unnoticed in the grief over Cordelia's death.