When Penny Goodwin shoots her husband in cold blood, there appears to be no motive. This is the most difficult and at the same time the easiest of murders to deal with. Penny Goodwin has murdered her husband – that is a clear fact. Why she has killed him is far from clear. When Hardy starts an investigation for the defence, he uncovers a most ingenious plot, which even Chief Inspector Fleming will not believe. Guest star David Langton, Robert James and Edward Dentith.