The case of the perjured parrot

When a wealthy man is murdered, his son asks Perry Mason to help find the murderer and keep the widow from taking control of the estate. The only witness to the murder is a parrot. The plot gets complicated when a second parrot is discovered which seems to name the killer, "Helen," -- the widow's name, but another Helen shows up, claiming she was recently married to the deceased man. Circumstantial evidence points to the second Helen as the killer, and Perry Mason sets out to clear her and locate the real murderer.