midnight
`` I know the chirp of every bird that belongs here . I shall know in a minute if anything happens that is unusual . '' `` And I 'll watch by the gate , '' declared Donald . `` Only till midnight , '' said Billie , `` when I 'll relieve you . '' `` And I 'll relieve the señora , '' said Josie . `` Where do I come in ? '' queried Mr. Black .