Back at Gloucester's castle, Gloucester unloads his heart to his evil-genius son, Edmund.
Gloucester is in a bad mood. He's upset about how unnaturally Lear's own daughters deal with the old King, and even more upset that they've taken over his house.
The sisters have instructed Gloucester not to mention Lear in their presence, on pain of "perpetual displeasure."
Gloucester then tells Edmund that he has received a politically explosive letter informing him that tension is rising between Albany and Cornwall.
More importantly, thanks to Cordelia, the French army is already poised to liberate Britain. (Remember, Cordelia ran away to marry the King of France after Lear disowned her in act one, scene one.) The French will also avenge Lear's wrongful treatment, which is good for everyone except Regan, Goneril, and their husbands.
In the meantime, Gloucester can't bear to obey Cornwall's orders – he's going to go find Lear and bring him relief with all this good news, even though helping Lear is grounds for serious punishment (death).
Before he leaves, Gloucester asks Edmund to cover for him if Cornwall asks where he is.
Edmund, being Edmund, says "yes" but immediately decides to betray his father to Cornwall instead.
That way, Edmund reasons, he can take over his father's wealth and position. After all, "the younger rises when the old doth fall" Edmund chortles. (Hmm. This sounds a lot like the motto of Goneril and Regan, don't you think?)