The Adventure of the Wary Witness - S1.E15

Ellery's old college chum, Linville Hagen, is accused of murdering mobster Nick Danello and Ellery must find a missing witness who can prove his innocence. This missing witness was a woman wearing a green dress. This description, of course, could fit any woman in New York. Ole Frank Flannigan comes along for the ride too and this time he's not quite so antagonistic towards Ellery.