Hamlet was a prince of Denmark.
After his father dies under mysterious circumstances, his sanity begins to decline. This is further strengthened by his mother, Queen Gertrude, marrying his paternal uncle, Claudius, an act generally condemned within their society.
His father comes to him in the form of a ghost, revealing the treachery behind his death: namely, at the hands of Claudius. Hamlet then pursues vengeance upon his uncle and mother. In his quest to seek vengeance, he inadvertently kills Polonius, the father of Ophelia, his betrothed. This deed sends her into a downward spiral, which ultimately ends in her death, a supposed suicide.
Claudius exiles Hamlet to England, during which he evades an assassination attempt orchestrated by his uncle. After this, he returns to Elsinore. There, Laertes, Ophelia's brother, attempts to exact vengeance upon Hamlet using a poison-tipped sword. During their mêlée, Hamlet manages to switch blades with Laertes, the end result being that they both have been pricked by the dosed tip.
During the spectacle of the two fighting, Gertrude inadvertently drinks from a poisoned goblet intended for Hamlet, dying herself. Hamlet, still alive but mortally wounded, exacts one last bit of vengeance upon Claudius before dying himself.
During the spectacle, Hamlet's mother inadvertently drinks poison intended for her son. Hamlet, still alive but mortally wounded, exacts one last bit of vengeance upon his uncle before dying himself, thus paving the way for Fortinbras to secure the throne.