As the saint walked home a dog would show up and frequently chase away criminals.
The work of St. John Bosco reforming young boys wasn’t highly regarded by many and in fact, Bosco’s life was openly threatened on multiple occasions.
To protect Bosco, God sent to him a dog to keep him company on his lonely walks home.
This is narrated in the 19th-century book Life of Don Bosco.
One night returning home later than usual and feeling vague apprehension [Bosco] saw a dog approach and felt alarmed, but the animal gently wagged his tail and turning, walked beside Don Bosco, who caressed him. All fear vanished. The dog escorted Don Bosco to the Oratory but refused to enter. Whenever he was late in coming home, on one side “il Grigio,” the grey [dog], appeared.
The dog not only accompanied Bosco, but also chased away criminals who tried to kill Bosco.
On [one] occasion Grigio defended Don Bosco from a formidable band of paid assassins. When at midnight passing through the Place Milan…he observed a man follow, armed with a large cudgel and hastened with the hope of reaching the Oratory safely. He was already at the top of the declivity when lower down he saw a group of men, then he waited for the one behind, whom he threw down. His comrades surrounded Don Bosco with raised sticks, the faithful Grigio appeared, beside his protégé, snarling and springing about in such fury that the wretches terrified besought Don Bosco to quiet the dog and vanished in the darkness. Don Bosco’s faithful four-footed guardian escorted him to the door of the Oratory.
This happened on multiple occasions, but the mysterious dog never stayed long at the Oratory, only appearing when Bosco needed him.
Where the dog came from remains a mystery, and some believe it may have been Bosco’s guardian angel in disguise.