In the climax of Harry Potter and the Chamber of Secrets, when Voldemort set the basilisk on Harry, Dumbledore's phoenix Fawkes suddenly arrived in the Chamber with the Sorting Hat, from where Harry pulled the Sword of Gryffindor and killed the basilisk.
The question is, as nobody knows where the Chamber was prior to Harry and Ginny opening it, how did Fawkes find out where to go to help Harry? Was it that the bird always knew where the chamber was? Or did Dumbledore send him to help Harry? If so, why did Dumbledore himself never come?