Pennington Barclay, master of Greengrove, is murderously attacked in his library by something that exits from a completely locked room. The entire household - including Pennington's beautiful young wife, and his nephew, who is the heir to Greengorove by virtue of a newly discovered will - is in an uproar. Estelle Barclay, Pennington's spinsterish and psychically inclined sister, insists the attack was the work of Greengrove's ghost. Enter Dr. Gideon Fell. Armed with his everlasting cigar and a wicked cane, this obstreperous extrovert succeeds in frightening everybody. For as horror piles on horror throughout the night, Gideon Fell evidences interest in one person only - the spirit of the long-departed Mr. Justice Wildfare. But Fell was not up to any supernatural hijinks, as someone well knew... the one who was most frightened of all.