A rich but disliked elderly man invites his relatives to a family reunion at his home. Once the gathering is complete, he announces enigmatically that he intends to change his will before he dies. Before he can do this, he is murdered. His niece (Gynt), a detective story writer, has to put her theories into practice by solving a real-life murder mystery.
The Robinsons are two respectable middle class parents living with their children in a suburban house in Acacia Avenue. Preferring to holiday every year in Bognor, they are pressed into booking a cruise for their annual vacation and thereby leaving their teenage children free run of their house. As the youngsters enjoy their newfound freedom and discover the angst of teenage life, Mr. and Mrs. Robinson begin to have second thoughts about their cruise and decide to return home early.
Ex-army private Randle stands to receive a substantial inheritance from his uncle if he can prove he is of sound mind. However, his devious cousin tries to grab the money by having Randle committed to a psychiatric home.
