The friar and Juliet can control their actions and decisions within the plan, such as Juliet taking the potion and pretending to be dead. They can also control how they communicate with each other to ensure the plan is executed smoothly. However, they cannot control external factors or other people's actions that may impact the outcome of the plan.
Balthasar ruins the friar's plan by beating Friar John to delivering the message of Juliet's fake death. By telling Romeo before the Friar it caused Romeo to believe Juliet was actually dead.
Juliet asked Friar Laurence to help her avoid marrying Paris by giving her a plan to fake her death so she could be with Romeo instead.
Friar Lawerence's plan was for Romeo to take Juliet away to Mantua with him where they could live together.
Friar Laurence asks Friar John to deliver a letter to Romeo explaining the plan to fake Juliet's death.
Friar Lawrence devises a plan for Juliet to fake her own death by taking a potion that will make her appear dead. Juliet is worried whether the potion will actually work, if she will wake up in the tomb alone, or if the potion might actually kill her.
Juliet threat to kill her self
She was anxious and desperate. If the Friar had not thought of a plan her intent was to kill herself, right there.
She threatens to kill herself.
Juliet's emergency with Paris.
The Friar's plan is to hide Juliet in the Capulet family tomb, where Romeo will later come to retrieve her once she awakens from the potion-induced sleep.
In scene 2 of Romeo and Juliet, the unseen occurrence that ruins Friar Laurence's plan is Friar John being unable to deliver the letter to Romeo in time. This prevents Romeo from receiving the message from Friar Laurence explaining Juliet's fake death plan, ultimately leading to tragic consequences.
Act IV Scene 1.