In his play Romeo and Juliet, William Shakespeare has created a complex tale of two lovers, their families, and the steps the lovers and others take in order for the two lovers to be together. Even though Friar Laurence chides Romeo for just declaring his love for Rosaline, he agrees to marry the two when Romeo declares his love for Juliet and she returns those feelings, and so he becomes their accomplice. He helps the two concoct a plan, whereby Juliet will partake of a sleeping draught that simulates her death, and after she is taken to the tombs he’ll send Romeo. Friar Laurence gives Friar John charge of delivering the letter informing Romeo of the plans. Unfortunately, Friar John finds himself unable to give Romeo the message as the town has been quarantined, and he couldn’t meet with Romeo. To compound this problem, Friar Laurence has difficulty finding the Capulet tomb where his is sure he’ll find Romeo, and he indicates this by saying, “Saint Francis be my speed! how oft tonight/
Have my old feet stumbled at graves! Who's there?” When he does finally arrive at the correct tomb, he is too late because Romeo has already consumed the poison he got from the apothecary.
The inconvenient "coincidence" which spoils the Friar's plan to help Romeo and Juliet live happily ever after is perhaps the most important dubious occurrence in the play. The Friar plots with Juliet for her to fake her death; part of his plan is for a messenger to travel to Mantua to inform Romeo that Juliet is not truly dead and to wait until all has passed with the funeral, etc., before trying to reunite with his young bride. However, when the messenger tries to go to Mantua, a plague has infected Mantua, and the messenger is not allowed into the city (which is, in a sense, under quarantine). So, Romeo does not get the message, ends up thinking Juliet is dead, and plans for his suicide.
Shakespeare's tragedies often rely on coincidences such as this one (the messenger just happens to arrive when a plague has attacked the city), and the audience is expected to suspend reality for overall dramatic effect. In this case, the tragic incident from Act 5 in which Romeo does not get the all-important message not only adds to the play's tension, but it also advances one of Shakespeare's themes--lovers controlled by fate. Because Romeo and Juliet are "star-crossed" lovers, no matter how either strategizes, the fates are against them.