ten o'clock
But silently . They entertained three couples at their house-warming party . It was a delightful party , a credit to Ben , Betty and the finest built-in house robots the mind of Amalgamated could devise . By ten o'clock they had dropped a dozen or more random hints , but never a sales pitch . Suspense was building nicely when Betty put down an empty glass and unobtrusively pushed the button to cue Nana . Perfect timing . They apologized to the guests , `` We 're ashamed to be so old-fashioned but we feel better if we look in on the boy when he wakes in the night .