Basil of Baker's Street, the masterful mouse detective who studied under Sherlock Holmes, is on his way to a school reunion with his old friends from Ratcliffe College. Along for the trip is his steadfast companion, Doctor Dawson. But all is not well, as they soon learn that the dastardly Ratigan has escaped from prison in London. Could the rat possibly be planning revenge against his old nemesis, Basil himself?

But before Basil and Dawson can worry too much about the wily rat, they hear another piece of worrying news. The duo arrives in Oxford only to be informed that the library of Basil's old college is haunted! The students are thoroughly spooked, and the whole mess threatens to sour the festive mood of the reunion. Basil, for one, doesn't believe in the supernatural and plans to put the rumors to rest.

But the strange occurrences continue, without any obvious explanation. Is this one case that can stump even the Great Mouse Detective? And as Basil and Dawson dig deeper, are there even more sinister secrets afoot?