nine P.M.
`` It is n't he , '' Harleston explained . `` He 's slender , with a mustache and imperial . It was Marston , likely . Did any of your officers see cab No. 333 between nine P.M. and this morning ? '' `` The reports are clean of No. 333 , but we are investigating now . It 's not likely , however . Meanwhile , if there is anything else I can do , Mr. Harleston -- '' `` You can listen to the balance of the episode -- beginning at half-past one this morning , when I found the cab deserted at Eighteenth Street and Massachusetts Avenue , with the horse lying in the roadway , asleep in the shafts ... '' `` What do you wish the police to do , Mr. Harleston ? ''