Doug Baily's father is weird, but a strange machine in the garage now makes him invisible too. It's a roller coaster ride of fun and hijinks as Doug tries to turn his invisible dad back to normal again.

One evening the Collins find their maid Mrs. Murdock at the end of their steps: dead, neck broken. Obviously she had an accident. Consequently they need a new babysitter for an upcoming big party. The sensible Helen meets little Susan Collins at the discount market and likes her, so she offers to do the job. She doesn't know Susan's teenage brother Mark - technically skilled and good in school, but restive and cunning. As soon as the parents have left, he starts psychologically terrorizing Helen and his sister with electronic tricks.