Descripción de editorial
A boy named Stuart is born to an ordinary family in New York City. He is normal in every way except that he is only just over two inches high and looks exactly like a mouse. At first the family is concerned with how Stuart will survive in a human-sized world, but by the age of seven, he speaks, thinks, and behaves on the level of a human of sixteen and shows surprising ingenuity in adapting, performing such helpful family tasks as fishing his mother's wedding ring from a sink drain. The family's cat, Snowbell, dislikes Stuart because while he feels a natural instinct to chase him, he is aware that Stuart is a member of the human family and thus off-limits.
On a cold winter's day, the family discovers a songbird named Margalo half-frozen on their doorstep. Margalo is taken in and spends the winter in the family, where she befriends Stuart; Stuart in turn protects her from Snowbell. The bird repays his kindness by saving Stuart when he is trapped in a garbage can and shipped out to sea for disposal. In the spring, when she is set free from the house, she continues to visit Stuart, infuriating Snowbell, who now finds himself with two small animals he is not allowed to eat.
Snowbell makes a deal with the Angora cat to eat Margalo to get rid of one of his temptations (reasoning that it's only wrong if he eats her). Margalo is warned in advance and flees in the middle of the night. Stuart is heartbroken but becomes determined to find her. He first goes to the local dentist, Dr. Carey, who is a friend of Stuart. The dentist's patient, Edward Clydesdale, suggests that Margalo may have flown to Connecticut, and Dr. Carey loans Stuart his motorized, gas-powered toy car for the long journey.
Stuart travels from adventure to adventure and finds himself in the town of Ames Crossing, where he takes work as a substitute teacher. There he learns that living in Ames Crossing is a fifteen-year-old girl named Harriet Ames who is the same size as Stuart but looks like a human being. Stuart purchases a miniature souvenir canoe, prepping it to make it comfortable and waterproof, and invites Harriet out on a boating date. However, when the two arrive for the date, the canoe has been discovered and played with by local children, who have ruined it. Harriet tries to be polite but is put-off by Stuart's sulking over his broken boat. Stuart decides to leave Ames Crossing and continue on his quest to find Margalo. He sets off once more in his car, thinking that he will never see her again.