Ellery Queen - The Adventure of the Eccentric Engineer

Author and amateur detective Ellery Queen attempts to solve another murder. When a once-brilliant, now seemingly senile inventor is murdered in his electric train workshop, the mystery is afoot. It seems no one could have come in or gone out during the period of time when the murder must have taken place, and a ticket was needed to gain admittance to the train room. This narrows the suspects down to his family and his business associates.