After learning from Albert that Sirius Black might have disguised himself as a black dog, Fred, George, and Lee Jordan often spent their free time wandering outside the Castle, trying to run into the black dog around Hogwarts. But this was undoubtedly a waste of time, as Albert never believed Black would show up around the Castle when it was crowded.
If Sirius Black's Animagus form had been a cat, there certainly would have been no need to worry about arousing suspicion. After all, a great many students brought pet cats to school, and having a few cats wandering around the Castle grounds was entirely normal. However, for another dog to appear around Hogwarts Castle seemed extremely suspicious, because aside from the bloodhound named Fang kept by Hagrid, almost no students brought dogs to Hogwarts.
Even so, Fred, George, and Lee Jordan never gave up the search for Sirius Black's whereabouts.
Chapter 690