A "proud, aloof man," Crooks is absorbed in rubbing liniment onto his crooked back when Lennie appears like a humble, ingratiating puppy in the doorway of the barn:
For a moment Crooks did not see him, but on raising his eyes he stiffened and a scowl came on his face.
Lennie smiled helplessly in an attempt to make friends.
You go no right to come in my room. This her's my room,. Nobody got any right in here but me.
After telling Lennie that he has no right to come into his room, Crooks tells him that he has no business in the barn since he is no skinner: "You ain't got nothing to do with horses." But, Lennie explains that everyone else is gone, and he has come "to see my pup." Against Lennie's "disarming smile" and childlike ways, Crooks condescends to let Lennie stay. Soon he realizes that Lennie is not capable of repeating what he says, so he opens up in their conversation having been lonely for such a long time.
He enjoys toying with Lennie to turn the tables, so to speak, since it has always been he who has been rejected: "S'pose George went into town tonight...[and]don't come back no more...Lennie gets worried, and then angered when Crooks persists in torturing him. When Lennie stands up and walks "dangerously" toward Crooks asking "Who hurt George?" Crooks realizes that he must desist.
Gently, he talks to Lennie, explaining that Lennie has George and he has no one. Expressing one of Steinbeck's motifs, Crooks tells Lennie,
A guy needs somebody--to be near him....A guy goes nuts if he ain't got nobody. Don't make no difference who the guy is, long's he's with you...I tell ya a guy gets too lonely an' he gets sick.
In his defensive pride, Crooks first rebuffs Lennie's attempt to enter the barn, then, he later reveals his angst: loneliness. This search for brotherhood is a motif of Steinbeck's "Of Mice and Men."