Sydney's colleague and ex Allan Devaut seeks her help as he was injected with a fatal poison and has only 24 hours to earn the antidote by bringing to tycoon's son Jean Chabot the Knight Templars' magical tau cross, found in 1099 in crusader kingdom Jerusalem, the cure for Jean's dying father Albert, who promises his empire to whoever brings it to him. Claudia is installed in the Paris library to continue research while Allan, Nigel and Sydney got look for the final clues to the cross in a medieval dungeon ruin and a modernized castle. They are bothered by rival relic hunter Van Gelden and Jean's henchman, and have reason to mistrust the cross itself.
—KGF Vissers