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.

Stink Moody, friends Webster and Sophie, and Mrs. Birdwistle visit tourist attractions in Virginia as they try to give away 101 guinea pigs rescued from a laboratory, although Stink is very reluctant to give away his favorite, Astro.

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.

When Stella gets the sudden idea to go caroling, she has a little trouble getting someone to join her. Her brother, Frank, is not good at spontaneity. The Watsons are very involved in a precarious fruitcake attempt (but happy to send their pig, Mercy, out for the occasion). Eugenia Lincoln declines, a bit rudely, to accompany on her accordion, and Horace Broom is too busy studying planetary movement. Will Stella need to sing by herself--with enthusiastic...