In past episodes, Mork has invited Susan Taylor, Sergei Krushev, and even a monkey named O'Keefe into the apartment against Mindy's preferences. This time, Mork invites a caterpillar, which he names Bob. And this time Mindy grants willing permission. Bob is a female caterpillar, which Mork can observe by looking at her figure, though he cannot tell her front from her back. Mindy walks into her bedroom, disinterested in playing with Bob.
Exidor comes to the door preaching a new religion, reincarnation. He believes himself once to have been Julius Caesar. Looking at Bob, he believes her to have once been Abraham Lincoln, for Bob doesn't give the appearance of one who would tolerate slavery. When Mindy re-appears, Exidor believes her to have once been Cleopatra.
Since Mork has no food for Bob, he calls on Bickley. Bickley believes that dogs are superior to caterpillars as pets, and gives several examples to press his point. When Mork asks for tolerance, Bickley concedes one practical use for caterpillars: they make great bookmarks.
Mork goes all out to accommodate Bob, building her a house, furnished with various attachments. But when he goes to show them to Bob, Mork finds Bob has died.
Mork calls on Exidor to revive Bob. Though he cannot bring Bob back to life, he does preside over her reincarnation as a cow living in India, where she will be held sacred. Since Mork thinks that Exidor has swiss cheese for brains, he asks Mindy's advice. She suggests a funeral.
Though she had something informal in mind, Mork makes his way to a mortuary. A cascade of misunderstandings keeps the funeral director unaware that Bob is a caterpillar. However, he does find it strange that the deceased is a female named Bob with no last name. He finds it odd that Mork is making arrangements though they only knew each other a few days, and that they were living together. When he quotes Mork a cost of $2,800, Mork decides to keep her with him, unburied. This nauseates the funeral director as Mork walks out.
Several weeks elapse with Bob in Mork's pocket, and Mindy persuades him finally to hold a funeral. Under the front of a cocktail party, they trick Bickley into attending too. Mork gives an ostentatious eulogy, and calls on Mindala McConnell to take a turn. After a half-hearted eulogy from Mindy, he calls on Bickley. Bickley resumes his thesis that dogs make better pets, and rushes out to take care of Bickie.
It's time for the burial, and Mork suggests Mindy's philodendron. When Mork retrieves Bob from the matchbox, she is missing, and a butterfly has taken her place. Finally impressed, Mindy tells Mork that the butterfly is Bob. The two of them release Bob out the window.
Mindy wonders if this gives Exidor's reincarnation thesis any credibility. But Mork still sees him as someone with his head stuck up his foot. They agree to follow Bob – Mindy through the door, and Mork through the window, until Mindy pulls him back in.
Mork reports to Orson about earth theories on the afterlife. He notes that Mindy believes in heaven. He explains that the reason earthlings don't want to die is that there are too many bugs in heaven. Orson asks Mork's opinion, but Mork doesn't know. All he knows is that, as Bob flew away, she looked angelic.