Irene's investigation has become too dangerous and must be stopped. Prisoners of the Germans, Gabriel and Djibouti receive help. The Sentinels will have to face the Übermensch, their most formidable enemy...

En route to free Mazauric, de Clermont is seriously wounded by a German patrol. Djibouti and Gabriel continue their mission without him and unknowingly grow closer to the Übermensch. In the laboratory, Marthe performs the first tests on the new recruit, Aria, a young woman sentenced to death whom she injects with the combat serum.

The Sentinels must free Mazauric, the mastermind behind the Dyxenal research, before he delivers vital information about the French serum to the Germans. At the Damned, the Baron receives a visit from Diane, a German spy who promises to find Gisèle if he helps her.

Irène investigates a news item involving Mirreau that appears to be linked to a state secret. At the cabaret "Les Damnés," the Baron discovers that Gisèle has run away. After the tragic loss of a comrade in arms, Gabriel wants to return to Paris to see his son and wife.

The General Staff orders the elimination of the German superman, who has become the Sentinels' main enemy. As they pursue him, the Sentinels are unaware that they will face the Übermensch, an adversary of immeasurable power.

Gabriel's wife, Irene, decides to investigate the cause of her husband's death. Captured by the French, Gruber, a German spy, is interrogated about the enemy program. Deployed on a mission, the Sentinels discover the work of a German soldier with formidable abilities.

Gabriel must join the Sentinels Brigade if he wants to see his family again, who believes him to be dead. After the attack of the secret military laboratory, an investigation is carried out, which does not please Colonel Mirreau, at the head of the program of the Sentinels...

In 1915, in the middle of the First World War, Gabriel Ferraud, a soldier of the French army, was wounded on the front. Rescued and evacuated, he was approached by army officials. He learns that he is selected to integrate an ultra-secret research project: the Sentinels program...