In what ways does Hazel's plan go wrong?

Hazel’s plan is to go to the farm and chew through the rope which holds the dog. Then, she and Dandelion will take turns luring the dog away in hopes of getting him onto the down where he will have free pick of Woundwort’s gang. Hazel's plans run amuck when a cat appears, pounces, makes the dog jump up and break its leash, and finally gets caught by the cat.