At one point Lennie tells George he can just go off if he likes because he is well able to look after himself if he wants to. Both George and Lennie know, however, that this is not true. Even with George looking after him, Lennie has the knack of getting into trouble (such as the incident at Weed, where he accidentally tore a woman's blouse). He needs George to guide him and to cover for him whenever he messes things up.
Lennie's dependance upon George, though, has its moments of "reprieve." Lennie has a one-track mind; he can do without George for at least one evening as long as he knows he will eventually be able to look after the rabbits when they get their own farm.
When George leaves Lennie to go "for a night on the town" with the other men, Lennie is not the only one left behind. Crooks, the Negro kitchen help, has also been left behind. Lennie sees a light on at Crooks' place and pays him a visit, preoccupied with the same idea. Candy, incidentally, has also decided to stay at the bunk house for the evening. Lennie tells Crooks why:
'All the boys gone into town, huh?'
'All but old Candy. He just sets in the bunk-house figuring.'
'Figuring?' What's Candy figuring about?'
'Bout the rabbits.'...'Bout the rabbits we're gonna get,, and I get to tend 'em, cut grass and give 'em water, an' like that.'
In his simple way, Lennie knows that their dream is now serious business since Candy has offered to pitch in his share to help buy the farm. He is as close as he will ever get to fulfilling his dream - having a place that belongs to him and having a place he belongs to.