Rudy's little sisters say there are 2 monsters in the kitchen. Who are they and what is the purpose of their visit?

Rudy is a young boy who, like many others his age, is being considered for education and training at a special school. Set in Germany in the 1930s–1940s, in a fictionalized town, this novel explores how Nazism affected children, who were too young to understand what was happening to their country. These “monsters” are Nazi Gestapo agents who have gone to Rudy’s family home to tell his parents that he should go to the Nazi school. In other places, they are called “coat men” for their appearance in long black coats.
While the children sit and play dominoes, the coat men/monsters intend to convince Rudy’s parents, the Steiners, boasting that the school is one the country’s “finest” for “elite” students to serve the Führer. Rudy has been identified because of his fitness and excellence at sports, but (we learn later) he does not identify with, or want to be part of, any “master race.” His parents are not swayed, and they refuse to let him go.