Richard III is the last of Shakespeare's four 'history plays' known collectively as the 'first tetralogy'.
Richard, having set his sights on being King of England, goes out to destroy anyone who stands in his way, including his brother King Edward IV. He turns his two brothers against each other and manages to persuade the king to send Clarence to prison, where Richard pays two executioners to kill him.
Richard dates the recent widow of the Prince of Wales and the pair marry. King Edward soon dies of ill health and Richard takes over as regent until Edward's sons come of age.
To 'protect' the young brothers Richard sends them to the Tower of London, where he then plans their murders, thus ensuring that he becomes King.
After his wife suspiciously dies, Richard turns his attentions to his own niece and goes about planning a marriage. King Edward's widow Elizabeth has arranged a match for her daughter with the Earl of Richmond, and battle lines are drawn as Richmond leads an army to overthrow Richard III.
The night before the battle begins the ghosts of all Richard's victims come to him and forecast his demise. During the battle Richard falls from his horse and is killed by Richmond during a sword fight. Richmond is crowned King Henry VII there on the battlefield.