ten o’clock
Mr. Lucas is an unmarried man , thirty-four years of age , and his establishment consists of Mrs. Pringle , an elderly housekeeper , and of Mitton , his valet . The former retires early and sleeps at the top of the house . The valet was out for the evening , visiting a friend at Hammersmith . From ten o'clock onward Mr. Lucas had the house to himself . What occurred during that time has not yet transpired , but at a quarter to twelve Police-constable Barrett , passing along Godolphin Street observed that the door of No. 16 was ajar . He knocked , but received no answer . Perceiving a light in the front room , he advanced into the passage and again knocked , but without reply .