"The Dark Pool" focuses on Dianne Castillejo (Lois Nettleton), the young mother of an adopted son who accidentally drowns in the family pool while she is occupied on the telephone conversing with her husband Victor (Anthony George). The coroner's final judgment is death by accident, but Victor believes that the child's nanny, Mrs. Gibbs (Doris Lloyd), is to blame for being negligent. Mrs. Gibbs, Dianne's nanny until age 12, and ever devoted to the grieving mother, is willing to take the blame so long as Victor remains unaware of Dianne's recurring alcoholism. Unfortunately, trouble starts when a strange woman (Madlyn Rhue) shows up on their doorstep, claiming to be the child's birth mother, and threatening blackmail to hide Dianne's drinking problem. Madlyn Rhue is best remembered for the classic STAR TREK episode "Space Seed," and the cast also includes David White (Darren's boss on BEWITCHED) and John Zaremba.