Future, Meet the Past

When Luffy wakes up on the Going Merry he's shocked. When the crew suddenly looks younger hes confused. When he sees Ace hes devastated. The crew find themselves appearing on the Merry in Alabasta, but how could this be? They were almost at Raftel, not Alabasta! And why was Ace suddenly... alive! How will they handle this, and more importantly, how will they get back to their time?