In Act 4, Scene 6, Oswald encounters blind Gloucester being led through the open fields near Dover by Edgar, who is pretending to be a crude peasant although he is actually Gloucester's son. Gloucester has been proclaimed a traitor, and a reward has been offered to anyone who kills him. Oswald says:
A proclaimed prize! Most happy!
That eyeless head of thine was first framed flesh
To raise my fortunes. Thou old unhappy traitor
Briefly thyself remember: the sword is out
That must destroy thee.
Edgar naturally intervenes, though he is armed only with a "ballow' or cudgel. Edgar kills Oswald and gets possession of letters Oswald was delivering to Edmund, Edgar's bastard half-brother, who has been made earl of Gloucester for informing against his father, who was communicating with Cordelia and the invading French army. The letters reveal that Goneril and Edmund are plotting to murder her husband Albany, enabling Edmund to marry Goneril and become a joint ruler of England. This discovery leads to Edmund's undoing as well as the suicide of Goneril, who had previously poisoned her sister Regan. Edmund, Goneril, and Regan all die. Regan's husband Cornwall had previously been killed by his servant in Act 3, Scene 7.
Albany is the only survivor of the four persons who received the joint rulership of Lear's kingdom at the beginning of the play. In Act 5, Scene 3, Albany says he will resign his power and turn it over to King Lear, who has been restored to his throne by his third daughter Cordelia and the invading French army. Albany restores Edgar and Kent to their rightful titles, Edgar as Earl of Gloucester, and Kent as Earl of Kent.
There are many deaths in this play--Cornwall, Oswald, Gloucester, Goneril, Regan, Edmund (killed in a duel with his half-brother Edgar), and Cordelia (a prisoner, murdered on Edmund's orders). King Lear himself will obviously be dying in a short time, and Kent says he expects to die at the same time as his master Lear.