Marilyn's boyfriend invites Marilyn and her family to a masquerade party.. Lily is Little Bo Peep, Grandpa is Napoleon, and Herman is dressed in armor. At the end of the night Herman with a prize for wearing a Frankenstein costume under his suit of armor. Lily and Grandpa feel insulted because that is Herman's real face!

Grandpa finds an ancient book of recipes ...including one for the "Love Potion". He mixes up a batch and the next morning he secretly spikes Marilyn's oatmeal, who is running late for work and leaves without breakfast. Lily empties her breakfast back in the pot and serves it to the rest of the family. Afterwards Lily and Herman find themselves the unwelcome targets of amorous advances made by their nosy neighbors.

Affected with a bad case of insomnia, Herman decides to go out for a walk in the local park. During his walk, a thief snatches a purse from a lone woman and disappears. At the same time a drunk and another woman see Herman in the park and call the police reporting a monster in the loose. The following morning Herman is confused by the newspaper count of the monster in the park. Not realizing that he is the monster, Herman finds police conditions deplorable and fails to understand how such things are allowed to happen.

Grandpa and Herman mistakenly get the idea Lily is pregnant after overhearing part of a private conversation between her and Marilyn. Marilyn works as a baby-sitter for another family and they have asked Lily if the little boy she minds can stay with the Munster family while his parents are away on vacation. Although Herman drops a number of obvious hints, Lily refuses to say anything about the new arrival.

The gas company wants to run a pipeline 25 feet under the Munsters' house. At that depth it would run through Grandpa's dungeon lab. When the workers are digging they get extremely frightened by Herman and Grandpa's appearance. Mr. Pike, the manager of the Gas Company, thinks its a good idea to visit with The Munsters to see what's going on...

Trouble begins in the Monster household when Herman tells Lily he intends to attend an Army reunion banquet wearing his old uniform. Lily is against the idea since Herman would have to spend the night away. However, she agrees, providing Herman will lose enough weight in the ten days remaining until the reunion to fit into his old uniform.