The Golden KeyKeepers of the Key #1af Lene Dybdahl

In the moonlight, the imagination comes alive...
When Laura and David’s parents are kidnapped, they must travel to Madrid in search of the mystical Golden Key.
It is a dangerous race against time, as they are being hunted by a sect of assassins, who will stop at nothing to get ahold of the key.
The Golden Key is volume one in the Keepers of the Key series. The twins, David and Laura, go on a journey, where riddles, prophesies, and magical objects open doors to other worlds … places they never imagined were real.