Lyle the crocodile lives in a house on East 88th Street in New York City. He likes it there, and his hosts, the Primms, like having him around--he helps young Joshua with his homework, jumps-rope with the neighborhood kids, and browses through antique shops with Mrs. Primm. Much to the affable reptile's dismay, however, he makes his neighbor's cat Loretta crazy, which in turn makes Mr. Grumps, Loretta's owner, even crazier.

One day, Mrs. Primm and Lyle are shopping, when Lyle--through no real fault of his own--ends up infuriating department-store bigwig Mr. Grumps who turns red and blue and purple with rage. This unfortunate eruption lands the rollicking reptile in the Central Park zoo where Lyle fights back his crocodile tears. In an elaborate sequence of events, Lyle finds himself back with the Primms on East 88th Street, a neighborhood hero, and, startlingly, even a friend of the mistrustful cat Loretta.