premise: The Highway of Hope is a 1917 American Western silent film directed by Howard Estabrook and written by Harvey Gates and Willard Mack. The film stars House Peters, Sr., Kathlyn Williams, Jim Farley and Harry De Vere. The film was released on May 17, 1917, by Paramount Pictures.
hypothesis: The Highway of Hope had five actors in it. 
reason: It said that it starred four actors, I know that, but in movies, there are often extras and other people who aren't considered stars. There could have been one more extra or small role, or not, there is no way to know for sure, which is why it could be either. Also, it said that it starred them, not that it didn't star anyone else. When you see them say a movie stars someone they don't list a huge cast with every extra... just the main people. 