Edward, Richard, and Hastings return to England with troops provided by Burgundy. They knock at the doors of the town of York. The mayor won't let him in, but Edward insists that he is at least the Duke of York. Then, he says he now supports King Henry, so the mayor lets him in.
Montgomery arrives, offering himself as an ally to King Edward. Edward says he only wants his title as duke for the moment. Montgomery says he'll take his troops away, then, for he wants to serve a king, not a duke. Edward says they must come up with a plan or wait until they are stronger before trying to regain the throne. Hastings urges him to strike immediately. Edward is convinced, and Montgomery declares himself Edward's champion. Edward thanks his supporters.
Henry enters with Warwick, Montague, Clarence, and Oxford. Warwick reports that Edward has returned from Burgundy with an army. He urges his lords to raise up armies. The lords take their leave of Henry.
Henry and Exeter talk. Henry says he thinks Warwick will beat Edward's army. Henry considers his reign as king, saying he has made an effort to answer the demands of the various nobility and the people, neither greedy nor oppressive; so why do some like Edward more?
Edward and Richard enter, with soldiers. Edward orders Henry captured and that he may once again be proclaimed king. He sends Henry back to the Tower and sends his troops to meet Warwick in the field.
Within Act IV, Edward has been king, exiled, and king again, while Henry has been imprisoned, crowned, and imprisoned again. This act's swift progressions through the various changes of state throw into relief how dizzying these changes must have been for citizens of the time.
As the audience struggles to keep up with the identity of the king and who is on which side, even Shakespeare may have become confused. Montague, never a very significant character, swore his allegiance to Edward right after George left to join Warwick's forces, yet by the end of this act, Montague shows up on Henry's side. Either he changed sides along the way to little fanfare, or Shakespeare shifted Montague around without noticing it, thus, demonstrating the confusion of allegiances in this civil war.