about three in the
morning
``` Never , ' said I. ``` I suppose that you could not possibly whistle , yourself , in your sleep ? ' ``` Certainly not . But why ? ' ``` Because during the last few nights I have always , about three in the morning , heard a low , clear whistle . I am a light sleeper , and it has awakened me . I can not tell where it came from -- perhaps from the next room , perhaps from the lawn . I thought that I would just ask you whether you had heard it . '