Beth, Calvin, and their son Conrad are living in the aftermath of the death of the other son. Conrad is overcome by grief and misplaced guilt to the extent of a suicide attempt. He is in therapy. Beth had always preferred his brother and is having difficulty being supportive to Conrad. Calvin is trapped between the two trying to hold the family together.

Four socialites unexpectedly clash: heiress Brooke Carter runs into gambler Johnny Spanish at the race track while playboy Michael O. Pritchard nearly runs into stage star Kitty O’Kelly with his car. Backstage at Kitty’s show, it turns out she and Brooke are old friends who attended public school together. The foursome do the town, accompanied by Brooke’s companion Elizabeth, who throws herself at Michael’s butler and chauffeur Rodney James.

An old-time movie-star singer/ hoofer rebonds with his estranged daughter and 9-year-old granddaughter.

Bill McKay is a candidate for the U.S. Senate from California. He has no hope of winning, so he is willing to tweak the establishment.

The story follows a family of inbreeds who have been afflicted by a genetic disorder known as ‘Merrye syndrome’, named after the family in which the disorder developed. This malady causes its victims to enter a state of age regression that starts at the age of ten and continues throughout the remainder of the person’s life, rendering them with the intelligence of a child. The final generation of the family has been entrusted to the care of the family chauffeur (Lon Chaney Jr), and all is well for these odd people until a greedy branch of the family decides that they want to relieve the family of its home. Mental illness has always, and will always be, a fascinating subject for horror movies as it probes into the unknown and Spider Baby makes best use of that fact.