Here is a brief plot summary of Henry VI Part 3:
The Yorkists are defeated at the Battle of Wakefield. Clifford murders York’s young son, the Earl of Rutland. Margaret and Clifford taunt the duke of York before killing him. The Earl of Warwick now takes York’s eldest son, Edward (King Edward 1V of England) under his wing. At the Battle of Twoton, they take revenge on Margaret’s army, and Clifford is killed. Following the battle, Edward is proclaimed king, and his two brothers, George and Richard, are created Dukes of Clarence and Gloucester respectively.
Warwick turns against Edward when he marries Lady Grey, and he changes sides, joining Queen Margaret and allowing his daughter to marry her son, the Prince of Wales. The Duke of Clarence goes over to Warwick, marrying his other daughter, and Edward IV is taken prisoner. He is rescued by his brother Richard and the faithful Lord Hastings.
King Henry VI has been restored to the throne, and the young Earl of Richmond (the future King Henry V11) goes into exile in France to escape the Yorkists. Edward defeats and kills Warwick at the Battle of Barnet. In a subsequent battle, he kills the Prince of Wales and captures Queen Margaret.
Richard of Gloucester begins his campaign to remove all obstacles in his path to the throne by murdering King Henry VI who is a captive in the Tower of London. Henry prophesies Richard’s career of villainy and his future notoriety. However, King Edward’s wife has just given birth to a son, the future King, Edward V of England, and the play ends here.