I assume you are referring to Macduff's plan to leave Scotland at his earliest convenience and seek assistance for Macbeth's overthrow. The plan is effective in the sense that firstly, Macduff, in leaving in such a hurry, denies Macbeth the opportunity to assassinate him as he had done with Banquo. Macbeth has been aware of Macduff's sentiments and knows where his loyalties lie and wants him dead. In fact, the murderers who kill Macduff's entire family come looking for him for, on their arrival, the first murderer asks Lady Macduff, "Where is your husband?" The murder of Macduff's entire family and his servants indicates how ruthless and bloodthirsty the tyrant has become. With his rushed escape Macduff had, essentially, abandoned his family and left them vulnerable and open to Macbeth's malice. In this regard, the plan was not entirely effective. In his defense, though, one can argue that he had no choice but to leave. If he had tarried, he would have...