Back at Gloucester's castle, Oswald reports to Cornwall that Gloucester has helped Lear and the Fool escape to Dover. He's apprehended Gloucester at the gate of his own castle.
Cornwall, Regan, Goneril, and Edmund plan how they will punish Gloucester. Regan suggests they hang him instantly, while Goneril suggests they pluck out his eyes.
Cornwall tells Edmund to escort Goneril back to her own castle (while Cornwall stays at Gloucester's castle). Cornwall explains that having Edmund in the castle while he tortures Edmund's father would be kind of inappropriate.
But before Edmund and Goneril leave, Oswald (Goneril's steward) comes in with the report that Lear is headed towards Dover, courtesy of Gloucester.
As Cornwall's servants drag Gloucester into the room, Gloucester protests that Cornwall and Regan are his guests, and this isn't a very gracious way for guests to act. Huh. You think?
Still, Regan and Cornwall haven't exactly been to charm school. They order the servants to tie him up. Then they berate Gloucester as a traitor, pull out some of his beard hairs, and demand to know where he sent King Lear.
Gloucester gets defiant. He attacks Regan and Cornwall for their immoral treatment of Lear. "I shall see / The winged vengeance overtake such children," Gloucester warns them.
"See't thou shalt never," Cornwall says coldly (but wittily!) before ripping out one of Gloucester's eyeballs.
Regan eagerly tells Cornwall to take out the other eye, too, but before he can do so, one of Cornwall's servants decides to rebel. He tells Cornwall he cannot watch him commit such an atrocity.
Cornwall's pretty upset about this, so he quickly draws his sword for a fight. The servant wounds Cornwall, but Regan stabs the servant in the back and kills him. Cornwall, panting, takes out Gloucester's other eye, calling it "vile jelly." Not the kind of "jelly" they put in delicious donuts.
Gloucester, now completely blind, calls upon his son Edmund for help. Regan informs him that it was Edmund who turned him in.
Gloucester has the epiphany that Edmund is a traitor, and has likely been a traitor from the start. More importantly, Gloucester realizes that Edgar must have been innocent.
Regan orders that Gloucester be put outside and abandoned to fend for himself. After a servant leads Gloucester out into the elements, Regan and Cornwall—about to collapse from his wound—stumble out as well.
The servants left in the room are shocked at what they have just witnessed. They decide they have to help the blind Gloucester.