In Harry Potter and the Prisoner of Azkaban, when the Dementors search the Hogwarts Express, Professor Lupin derisively says that none of them in the compartment are hiding Sirius Black in their robes.

But Ron has Scabbers in his robes, not knowing his “pet rat” is the actual murderer who committed the crime Black was wrongly imprisoned for!

If they were looking for the fugitive mass murderer, they were in the right place after all.