The idea for the movie grew out of two murder games I devised some time ago. One was for Phyllis Newman; the other for four couples just after I got out of college. A murder game? No, nobody gets murdered. With the four couples, I told each person to think of a way to kill one of the others over the weekend we would be spending together in the country. Then we passed out envelopes and inside one was an 'X'. That person was the only one who was to carry out his plan; the others were to spend the time avoiding being murdered.