Sentence:  The story struck the depressingly familiar note with which true stories ring in the tried ears of experienced policemen....The second note, the high alarum, not so familiar and always important since it indicates the paramount sin in Man's <WSD>private</WSD> calendar, took most of them by surprise although they had been well prepared. 
Meaning of the word marked with <WSD> tags:  Not publicly known; not open; secret.