Eimar Ultan O'Duffy (1893 – 1935) was an Irish writer, economist and satirist.

"The Mystery of the Octagon Room" is a story about a man who is invited to a remote country house, recently inherited by friends of his.

Many of the rooms in the house are rumoured to be haunted. But an unassuming octagonal room in the tower hides a particularly gruesome and terrifying secret. Nobody can stay there overnight - and those who have tried it were insane by morning. The narrator of the tale cannot resist the challenge and orders a bed, lamps and an oil stove to be installed in the Octagon Room, so that he can put the tale to the test.