In chapter two, Steinbeck introduces the reader to the laborer Carlson when the men come back to the bunkhouse after working in the fields. Carlson is interested in having Slim give Candy one of his newborn puppies. Carlson claims that Candy's dog should be put down because it is old and decrepit. He tells Slim,
"That dog of Candy’s is so God damn old he can’t hardly walk. Stinks like hell, too. Ever’ time he comes into the bunk house I can smell him for two, three days. Why’n’t you get Candy to shoot his old dog and give him one of the pups to raise up? I can smell that dog a mile away. Got no teeth, damn near blind, can’t eat. Candy feeds him milk. He can’t chew nothing else.”
In chapter three, Carlson again brings up the subject and tells Candy that he should shoot his dog. Candy, who raised the dog from a puppy, is hesitant and not willing to part with his friend. Carlson is relentless on the subject and eventually gets the approval of Slim, who also believes the dog should be put down. He says,
“Carl’s right, Candy. That dog ain’t no good to himself. I wisht somebody’d shoot me if I get old an’ a cripple.”
Since Candy is unwilling to kill his own dog, Carlson volunteers and produces a Luger pistol. He tells Candy that he'll shoot the dog in the back of the head so that it won't feel any pain. He then takes the dog from Candy and soon a gunshot is heard in the distance. Candy is obviously distraught, and later in the chapter confesses to George that he should have shot the dog himself. The dog is symbolic of the fate which awaits anyone who has outlived their purpose. It is likened to Candy, who is also old and crippled. He admits that he will soon be "canned" from the ranch when he can no longer "swamp" out the bunkhouse and is eager to go with George and Lennie to the dream farm, which represents a sort of paradise for working men like Candy.
Carlson says that he will shoot Candy's dog in the back of the neck where the neck and head meet. If he shots the dog at this place, he tells Candy that the dog won't feel anything. He won't know what hit him. Candy suggests doing this because the dog is old, smells, and is crippled. Carlson says the dog isn't good to himself or anyone else. He believes that dog is suffering, but Candy says that he has had hin so long that it is hard to get rid of him. Candy's dog is his best companion.