midnight
`` In the stillness , very faintly , _ they rustled _ ! '' Silence fell . A car passed outside in Half-Moon Street ; its throb died away . A clock was chiming the half-hour after midnight . Dr. Cairn spoke : `` Anything else ? '' `` One other thing , sir . I was gripping the chair arms ; I felt that I had to grip something to prevent myself from slipping into madness .