a quarter past six
`` I still had to learn , in addition to the name of the assassin , which I did later , the time of the original attack . I learned this from the examination of Mademoiselle Stangerson and her father , though the answers given by the former were well calculated to deceive the examining magistrate -- Mademoiselle Stangerson had stated very minutely how she had spent the whole of her time that day . We established the fact that the murderer had introduced himself into the pavilion between five and six o'clock . At a quarter past six the professor and his daughter had resumed their work . At five the professor had been with his daughter , and since the attack took place in the professor 's absence from his daughter , I had to find out just when he left her . The professor had stated that at the time when he and his daughter were about to re-enter the laboratory he was met by the keeper and held in conversation about the cutting of some wood and the poachers . Mademoiselle Stangerson was not with him then since the professor said : ` I left the keeper and rejoined my daughter who was at work in the laboratory . '