Popular historian Doherty adds another inveterate rogue to his roster--English forger Ralph Croft, who scampers across the Channel and soon finds himself incarcerated in the Bastille, where his release is contingent upon his working with the Regent's men, archivist Maurepas and Captain D'Estivet, to discover the identity of the Man in the Iron Mask. False clues lead them to deduce that ""the mask"" was Eustace D'Auger, whose father was a musketeer and whose mother served the Queen. Further investigation by Croft, however, is hampered by threats from the secret order of the Templars; a code in the royal letters of Anne of Austria; and the fact that all of the jailers of ""the mask"" are long dead. The name on the death certificate (""Marciel""), combined with the closeness of Anne and a church cardinal, convinces Croft of the real identity--but a harrowing session with the Templars (and more incarceration) commands his silence. Less lively than other Doherty outings, but more factually compelling and the ending twist is a beauty. Like Tey's The Daughter of Time, this may become a history-class staple.