Hamlet's Uncle King Claudius announces his marriage to Hamlet's mother Queen Gertrude. Hamlet is not pleased with this decision, he is still mourning the death of his father.
Hamlet
Queen Gertrude
King Claudius
Act I, Scene ii
Ghost of Hamlet's father
The Ghost of Hamlet's father asks Hamlet to avenge his murder committed by King Claudius, Hamlet's uncle.
Hamlet
Act I, Scene v
Hamlet makes Horatio and Marcellus swear upon his sword not to tell a soul what they saw or heard regarding the Ghost.