about ten o'clock
If she lets you in , all right ; have a talk and see what comes of it . If she wo n't let you in just come down again and let us know , and then we 'll think what 's to be done next . '' This suggestion was approved , and time went on as the three discussed the mystery from every point of view . At about ten o'clock Mrs. Bubb 's ear caught the sound of a latch-key at the front door . She started up ; her companions did the same . By opening the door of the parlour an inch or two it was ascertained that a person had entered the house and gone quickly upstairs . This could only be Polly , for Mr. and Mrs. Cheeseman were together in their sitting-room above , their voices audible from time to time .