What happens in chapter 10 of Mrs Frisby and the Rats of NIMH?

In Chapter 13 of Mrs. Frisby and the Rats of NIMH (A Powder for Dragon) Mrs. Frisby is still shocked about the rats and their sophisticated advancements. She also learns that the rats put sleeping powder in Dragon's bowl to enable them to 'work' which causes Mrs. Frisby to recall her seeing the rats move a cable into their rosebush/cave.