On Darrin's birthday, Maurice drives in majestically through the wall and gives Darrin a multi-purpose lighter. Learning it contains magic, Darrin refuses it. Telling Samantha he's a jackass, Maurice turns him into a mule and vanishes in a puff of smoke. Gladys sees the mule but her husband stays with his crossword puzzle. When Samantha admits there is a mule in her kitchen, Gladys, protesting it's unsanitary, decides to call the authorities. Samantha appeals to her mother, but Endora insists it's strictly Maurice's affair. She zaps them to Paris where Maurice is entertaining Yvette and Angelique. He coldly suggests Darrin pull a wagon but relenting, snaps them back to the Stephens' house. Finding that Darrin has been removed to the animal shelter, Samantha retrieves him and demands that Maurice change him back. Failing, Maurice decides mutual concentration will help. Gladys sees Maurice playing chess with the mule. Deciding to recreate the whole event, Maurice reverses everything. The mule disappears and Darrin is back. Later, Abner asks about a sanitarium for Gladys who reported the chess playing mule. Rising to the challenge, Maurice turns himself into a mule to play chess with Abner.