We return now to the problem with which we opened the chapter. Recall that our task is to write a script for a television detective who is confronted with a murder mystery, the solution of which may depend on determining the time at which the murder was committed.

Here are a few more details. The discovery of the industrialist's body is made by his loyal and devoted secretary when she reports for work as usual at 8:30 A.M. She promptly calls the police, and our hero is on the scene in minutes. The secretary has not seen her boss since Friday afternoon, and (we will learn later in the show) no one else is willing to admit having seen him over the weekend. Everyone but the secretary hated this man, so there are lots of suspects.

The office building is located in Crystal City, a section of Arlington, Virginia, just outside of Washington, DC. Here are some of the people who had or may have had access to the building between Friday afternoon and Monday morning:

• The janitorial crew that works an 11 P.M. to 7 A.M. shift each night, Sunday through Thursday.

• The industrialist's ex-wife, who, unknown to everyone (except the detective, who has ways of finding out), still has a key to the building. Her whereabouts over the weekend cannot be accounted for, but she is known to have reported for work at 9 A.M. Monday at her regular job — in Cleveland.

• The industrialist's trusted but incompetent nephew, who had been given a managerial job in the firm, and who would inherit a large share of the fortune. His tennis partner confirms his presence on the tennis court most of Saturday. He (the nephew) says he went sailing alone all day Sunday. His wife claims he was in bed with her from midnight Sunday to about 9 A.M. Monday. He normally showed up for work between 10 A.M. and noon.

• The vice-president who is the real brains and the principal operating officer of the corporation. She is known to have rejected advances from the industrialist (when he was still married) and still to have advanced to the top on sheer determination and talent. She is also known to have a fixed work schedule of 6:30 A.M. to 6:30 P.M. six days a week — every day but Sunday, which she devotes to church and social activities. She was at work two hours before the secretary came in and discovered the body, but her usual practice was not to go near the owner's office, because he would always waste her time with off-the-wall ideas that would have been detrimental to the firm.

Note 1 – Source