Read the full text of Henry VI Part 3 Act 4 Scene 3 with a side-by-side translation HERE.
Three watchmen stand outside Edward's tent. They fear that Warwick is nearby, and that he wants to attack Edward.
Turns out they're right: Warwick, George, Oxford, Somerset, and their soldiers enter and take over the guards. Richard and Hastings make a run for it, but Edward is captured.
Edward tells Warwick that he just called him king not too long ago. Why is he capturing him now?
Warwick says that for one thing, Edward doesn't stick to his word. He's angry that Edward promised to marry Lady Bona and then went and had a quickie marriage with Lady Grey behind his back. Plus, even Edward's brother is against him now.
Warwick takes off Edward's crown and says he'll give it to Henry. Just like that.
Warwick and his men lead Edward out, but not before Warwick tells us that his plan is to free Henry from prison and seat him back on the throne.