Doors -!

Bestselling author Markus Heitz invites readers on an action-packed mystery adventure across three captivating alternate worlds - decide for yourself which world you want to experience first: "DOORS ?", "DOORS !" or "DOORS X"? Three books, three worlds, three doors - which will you open? Behind these doors lies much, including adventure. The wealthy father of the missing Anna-Lena van Dam sends ex-soldier Viktor with a five-member geo-expert team to search for his daughter. In a gigantic cave system, the group discovers several doors with mysterious symbols. To save Anna-Lena, they must embark on paths beyond science and reason - one of the doors takes the group straight into the 1940s. However, in this world, Nazi Germany capitulated early, the USA has taken colonial-like control over Europe, and threatens the resistance.