eleven o’clock at night
The time when it was bought shows it could not have been in the murderer 's possession . '' `` The time does n't worry Larsan . He is not obliged to adopt my theory which assumes that the murderer got into `` The Yellow Room '' between five and six o'clock . But there 's nothing to prevent him assuming that the murderer got in between ten and eleven o'clock at night . At that hour Monsieur and Mademoiselle Stangerson , assisted by Daddy Jacques , were engaged in making an interesting chemical experiment in the part of the laboratory taken up by the furnaces . Larsan says , unlikely as that may seem , that the murderer may have slipped behind them . He has already got the examining magistrate to listen to him .