Answer:
The mood is ominous and foreboding.
Step-by-step explanation:
George is crying over his dead puppy in the barn and Curley's wife walks in. They are alone and all the men are busy playing horseshoes. Curley's wife is lonely and Lennie is frantic because he thinks George will be angry (he can't tend the rabbits). This whole situation is like a tinderbox waiting to explode.