In the same vein as Cain and Abel, here we have two brothers, one a renegade cop and the other a murderer with a taste for little boys. The brothers come to blows, from which only one can walk away.
In this Dan Curtis production of the Robert Louis Stevenson classic, Jack Palance stars as Dr. Henry Jekyll, a scientist experimenting to reveal the hidden, dark side of man, who, in the process of his experiment, releases a murderer from within himself.
Two years of deterioration sees John and Barbara Lomax's marriage reduced to bitter sniping and "keeping up appearances" for the sake of the children. When John's old friend Bill professes his love for Barbara, the marriage finally breaks up – causing their three children to react in different ways and their son secretly determined to do Bill harm.