* The letter doesn't reach Romeo: He sends Friar John to Verona to deliver a letter to Romeo explaining Juliet's staged death and the plan to reunite them. However, Friar John gets quarantined due to a plague outbreak, and the letter never makes it.
* Juliet awakens to find Romeo dead: Friar Lawrence arrives at the tomb just as Juliet awakes from her drug-induced sleep. Romeo is already dead, having poisoned himself believing Juliet to be truly dead.
* Juliet takes her own life: Despairing at the loss of Romeo, Juliet stabs herself with his dagger.
* Friar Lawrence's guilt and despair: He witnesses the tragic outcome of his plan and his own failure to prevent it. He is consumed by grief and guilt, blaming himself for the deaths of Romeo and Juliet.
Essentially, Act 5 forces Friar Lawrence to face the consequences of his actions and the limitations of his influence. He is overwhelmed by the tragedy he couldn't prevent.