Far from being the best in the series

Beginning 1900, Veronique Hergemont marries on a whim and against the advice of his father to Count Alexis Vorski. Their relationship turns into a nightmare that will lead to the dramatic loss of his father and his son. 1917, when the Count Vorski was likely killed in the war in inglorious circumstances of Véronique Hergemont, by an extraordinary coincidence, is found in Brittany in search of his past. But the worst is yet to come ...

The plot is quite fine and well built (I especially appreciated the mechanism that leads to Véronique Hergemont to Sarek), the explanation of the mystery, which plunges us into the nascent physics of the interwar period, remains rather credible . The character of Arsene Lupin is very far it reaches the end as a "deus ex machina" just to unravel the mystery with a more stylistic than credible facility (the novel first appeared in the form of a soap opera This may be an explanation). The end is idyllic, worthy of the best novels in rose water. Moreover, as unfortunately often with Maurice Leblanc characters are caricatures: on-empathy with the right talents and possessing magnanimity and extreme detestation of evil to which no default is spared.
Note that the television adaptation (The Coffin Island - Edition 2 DVD), lack of fidelity to the book claimed, is also of poor quality.