The Clue of the Savant's Thumb (S04E09)

Jonathan Creek returns to investigate some seemingly supernatural events at a girls’ boarding school and the miraculous disappearance of a body in front of several witnesses. But as Jonathan and Joey soon discover, there is more to this case than a mere locked-room mystery – what is the link with the baffling red rings which appeared on the foreheads of convent schoolgirls in the 1960's, and the horrifying, ghostly death of a student? (iTunes)