Solution: Murder of a Mathematician

“It’s rather simple,” continued Sherlock. “The door to Desmond Clark’s office was confirmed locked by both Stephen and Lee. The key was found in the pocket of the late professor’s jacket. The only way that key could be there is if it was placed in there after the door had been broken down. There is no way the door could have been locked from the inside.

But who then placed the key in the professor’s jacket pocket? It must be the criminal! Who had the opportunity to do so? Both Stephen and Geraldine had spent time alone in the room¸ whilst Lee had not entered the room at all after discovering the body. Thus, we can eliminate her from suspicion.

Now remember, Geraldine entered the room later, holding in her hands a cup of tea and a snack (later confirmed to be a toasted cheese sandwich) which she had taken directly from the tea room. It would be incredibly difficult for her to swiftly and discreetly retrieve the key hidden on her person and then place it in the deceased’s pocket, when both her hands were occupied. Thus we come to the person who had the opportunity to do so – Stephen! The person who was kneeling by the body and would not draw any added attention.

Here is what I believe happened. Stephen was rifling through the desk of Desmond Clark, hoping to find some evidence that would incriminate him for plagiarism – a serious crime that could end his academic career. Perhaps it was a letter Desmond had written to the Dean? I do not know. Anyway, whilst Stephen is searching for this, Desmond returns early and sees his colleague. There may have been an argument, a plea from Stephen, but there is no fight. Desmond calmly reaches for the phone to call security. Stephen, in a moment of panic, grabs the letter opener from the desk and stabs Desmond in the back. The professor falls to the floor, the wound is fatal. Stephen quickly grabs the incriminating documents, and in his haste, knocks over a pile of papers to the floor. He locks the door of the office behind him, hoping it will buy him some more time.

Unfortunately, he hears footsteps coming up the corridor. He quickly makes it to his office door just as Lee turns the corner. When Lee tells Stephen she has heard some noises coming from Desmond’s office, Stephen quickly agrees and pretends that he had just come out of his office to also investigate. And the rest, you know.”