The case of the elevator duck by Berends, Polly Berrien published by Random House

What does a young detective do when he finds a lost duck in the elevator of his housing project? Elementary: he tries to find the duck's owner. But if No Pets Of Any Sort are allowed in the projects, who is going to admit he's lost a duck? Detective Gilbert doesn't even dare to tell anybody he has found one! How Gilbert cleverly solves these problems and the case, makes a humorous story of detection and city life.