Final answer:
In the play Macbeth, Lady Macbeth murders King Duncan and takes the crown with the help of her husband, Macbeth. This murder sets off a series of tragic events in the play.
Step-by-step explanation:
The murder of King Constance and the usurping of the crown is depicted in the play Macbeth by William Shakespeare. In the opening scene, Macbeth and Lady Macbeth conspire to kill King Duncan and seize the throne. Lady Macbeth takes an active role in planning and executing the murder, while Macbeth carries out the act. The murder sets off a chain of events that leads to the downfall of both Macbeth and Lady Macbeth.