Decent episode, very preditable though. A lot is giving away when the Grandmother died and Rod Serling's introduction about life and death. Of course we get the feeling we will be hearing from Grandmother again and we do.
Billy Bayles (Billy Mumy) claims he can talk to her on his toy phone. Everyone thinks he's traumatized until the mom hears the Grandmother. Then Billy in his rage when mother tries to stop his conversation falls into the pond and appears to be dying. The twist at the end with the Dad talking on the phone asking his mom to give him Billy back was predictable but still well executed.
One of those happy endings for the show.