The setting is Gloucester's castle. Oswald reveals to Regan that Albany's forces have been deployed, but with much reluctance. Regan is more interested in the letter that Oswald carries from Goneril to Edmund. Regan insists that the letter be given to her, because she is aware of Goneril's amorous glances toward Edmund. Regan tells Oswald that Edmund is to be reserved for her, since she is now a widow. Regan also directs Oswald to kill Gloucester if he finds him.
Albany's reluctance to support his wife's cause is clear as he reluctantly leads his army in defense of the kingdom. Oswald responds to Albany's hesitation by asserting that Goneril is the better soldier, which subordinates Albany's masculinity to his wife's powerful will. Oswald, however, is not accustomed to thinking about the morality of issues. As Goneril's servant, he accepts her orders without question.
Ironically, Regan expresses concern that Gloucester be relieved of his misery, especially since she is directly responsible for that misery. Her "pity of his misery" (IV.5.12) indicates that she is cognizant of public opinion and interested in her subjects' support of her actions. But, Regan does not devote much attention to this consideration; after all, she has already dispatched Edmund to kill his father. Instead, she is concerned with the letter that Oswald is carrying from Goneril to Edmund. Obviously, Regan suspects Goneril of having feelings for Edmund, and the attempts to force Oswald into surrendering the letter lack any subtly. Regan implies that she and Edmund have an understanding, and she hints that their relationship is more than casual.
By the end of this scene, the audience knows that Goneril and Regan are no longer working partners; instead, they have become rivals, engaging in hidden truths and plots. The sisters' competition for Edmund indicates that he is no longer simply the bastard son of Gloucester. Two royal princesses are vying for Edmund's attention, thus legitimizing his new position. At the conclusion of their meeting, Regan, who has already sent Edmund to kill Gloucester, now tells Oswald to kill the old man. She clearly does not want to take a chance that Gloucester might survive to reveal what happened to him.
nighted made dark; black.
belike quite likely; probably.
of her bosom have her trust or confidence.