After Mercy the pig snuggles to sleep with the Watsons, all three awaken with the bed teetering on the edge of a big hole in the floor.

Mr. Watson's usual Saturday drive in his Cadillac with his favorite pig, Mercy, turns into an adventure when an unexpected passenger shows up in the back seat and Mercy finds herself behind the wheel.

After Mercy Watson follows the delightful scent and delicious taste of the pansies her thoughtful neighbors plant to beautify their yard, animal control officer Francine Poulet is called out to handle the case, which brings unexpected results.

Features an audio read-along! When the Watsons decide to zip their porcine wonder into a formfitting princess dress for Halloween – complete with tiara – they are certain that Mercy will be beautiful beyond compare. Mercy is equally certain she likes the sound of trick-or-treating and can picture piles of buttered toast already. As for the Lincoln Sisters next door, how could they know that their cat would lead them all on a Halloween "parade"...