This quest has been removed from RuneScape, this guide is left as a reminder of the past.
Map-
Forbidden Love-
To start Romeo and Juliet you must talk to either Romeo or Juliet, for the purpose of this guide we will be starting with Romeo. Head to Varrock Fountain and speak to Romeo, tell him you have seen Juliet and agree to bring her a message. After a slightly lengthy conversation, you will be able to continue to Juliet’s house, located directly west of Varrock. Once you get to her house, go upstairs and speak to her. You will be given a message to take back to Romeo. Go back and speak to Romeo, you will found out that Juliet’s father opposes their marriage and Father Lawrence may be able to help.
A Deadly Plan-
You can find Father Lawrence in the church east of Varrock Castle. He will complain about you interrupting his sermon, only for you to point out that everyone is asleep. Father Lawrence will tell you that he has an idea of how to rescue Juliet. By giving her a potion to make her appear dead, she would be taken to the crypt where Romeo could rescue her. He will then tell you to ask the Apothecary for a Cadava Potion.
Foraging-
Head to the apothecary, he will tell you that he has all the ingredients needed except Cadava Berries. You can either buy Cadava berries from the Grand Exchange or pick them from the Cadava bushes below Varrock. Go talk to the Apothecary again and he will hand you the Cadava Potion.
Betrayal-
Now head back to Juliet and talk to her, she will head out to the Balcony and drink the potion. She will faint and be taken to the crypt. Now go back to Romeo and talk to him, you will head back to the crypt with him. Juliet will be lying on a stone block, Romeo will walk over to her and decide that she is dead. Then Phillippa will appear and “win” over Romeos heart.