midnight
`` But how , '' asked the King , `` during my vigils shall I know when midnight is due ? '' `` In the third quarter after eleven a bird sings . At the beginning of its song go forth from the Ring , and at the ending plunge your head into the Pond . For on these nights the bird sings ceaselessly for fifteen minutes , but stops at the very moment of midnight . '' `` And is this really all ? '' `` This is all . '' `` How easy it is to become good , '' said William cheerfully .