A retired surgeon, Jack, set up to investigate the murder of his son Stewart for which new evidence has emerged. Jack senses the opportunity to emulate the investigative detective works of his departed father but soon learns the difficulty of such a job. On a hunch, Jack actively pursues a wrong suspect. A potential blackmailer who began leaning on Jack's wife. In maneuvering to do his investigation, Jack uncovers more and more clues leading to his daughter-in-law Anna as the real murderer. Although she can have a hot temper, Anna is an excellent chemist researching toxic compounds.

Having a larger-than-life ego and her need to be loved, Anna has poisoned her husband Stewart, Jack's son, as he was walking out on her for another woman. Jack may be unprepared for what Anna has in store for him as she corners Jack into almost lethal violence, whereupon a scuffle between her and Jack's devoted wife saves his life. Half Hearted about his ability to do the job, Jack's wife had been trailing him all along his quest. Jack confesses to his wife that his son's life insurance company had hired him as a national investigator on this case and the company still needs his help on future cases. The wife agrees on the condition that they do this together.