Book 18: Map of Bones

Map of Bones by Rollins is the second novel in his Sigma Force series. In a horrific heist, a group of men march into a cathedral in Cologne, Germany, kill the church members by some mysterious means seemingly contained in the communion bread, and gun down the remaining children and non-Catholics in cold blood leaving with only the bones of the Magi. The Vatican is in an uproar after the brutal attack and dispatches Vigor Verona as a representative with his niece Rachel, a lieutenant in Rome's carabinieri, to meet with a trio of Sigma Force agents led by Grayson Pierce. No sooner does the group begin its investigation at the cathedral than they are ambushed by members of the Dragon Court, who are responsible for the original massacre. The two sides race to uncover an ancient secret power to either save the world or enslave it.

Map of Bones is another action packed adventure from start to finish. The Dragon Court itself and the character of Raoul in particular are more evil and insidious than the Guild of book 1, so I won't be passing this series onto my teenagers. I would consider it appropriate for ages 18 and up.