The dog called Capitan, a German Shepard, had disappeared from his home in the small town of Villa Carlos Paz in the centre of Argentina following the death of his owner, Miguel Guzman, in March, 2006.
Nobody in Guzman's family noticed the absence of the dog for days, until the members visited Miguel's grave at a municipal cemetery.
"Damian (Guzman's son) started to shout that it was Capitan and the dog came toward us barking, as if he were crying," the New York Daily News quoted Guzman's wife, Veronica Moreno, as telling the La Voz del Interior.
Capitan didn't impress Moreno but seeing how faithful he has been changed her mind.
Even though the family wanted to take the pet back home, he stayed by his master's grave.
What surprised the family was that Miguel had passed away in a hospital in the city and his body was taken to a funeral home far away from their residence and none of the members recalled the dog following them to the cemetery before.
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"The next Sunday we went to visit Miguel's grave and the dog was there. This time he followed us when we returned, because we had walked. He stayed with us at home for a while but later went back to the cemetery," Veronica said.
Capitan has made that cemetery his home for the past six years. Every day at 6 pm (local time), he lies down beside the grave of his master.
Veronica said that she didn't really like the dog when he was living with her and even when he was brought home as a gift, the woman thought he would cause too much extra housework.
But now that she's seen the dog stand so loyally by her husband's grave, she says she views the mutt more sympathetically.
The municipal cemetery's director, Hector Baccega, said that the dog has a special sense for Miguel and a very particular schedule.
The first time Baccega saw the dog, he arrived at the cemetery alone. The dog then did a couple of laps around the place before finding his master's grave - all on his own.
"And that's not all," Baccega said.
"Every day, at six in the evening, he lies in the front of (Miguel's) grave," he said.