in chapter one, lennie and george are on their way to a ranch to hopefully get a job. we learn that lennie is strong and always accidentally hurts people and things. he finds a little mouse and while he is carrying it around, he accidentally crushes it.
in chapter two, the men arrive on the ranch and meet all of the workers there. one of the workers has a very pretty wife that lennie has a liking to. the worker and lennie don't get along so we can expect a fight or other troubles coming.
in chapter 3, lennie is given a little puppy and spends all of his time with it. we already know that lennie is not gentle enough with little things so this could end badly.
another scene in chapter 3 is the killing of candy's dog. candy's dog was old and stinky. the dog never helped out around the ranch so carlson says they should shoot it and put it out of its misery.
also in chapter 3, george talks to candy about his dreams of owning his own farm. this shows us that george is starting to open up to candy and they are becoming closer.
the last scene in chapter 3 is lennie and curley getting into a fight. lennie is happy and smiley because he is thinking about living on his own farm and curley thinks he is laughing at him. curley throws punches and starts hurting him.