In the climax of the movie Harry Potter and the Chamber of Secrets, when Voldemort set the basilisk on Harry, the phoenix of Dumbledore, Fawkes suddenly appears in the chamber with the sorting hat, from where harry took out the sword of Gryffindor and killed the basilisk.
The question is, as nobody knows where the chamber was prior to Harry and Ginny, how did Fawkes find out where to go and help Harry? Was it that the bird always knew where the chamber was? Or did Dumbledor send him to help Harry? If so why did Dumbledor himself never come?