The Ryder

In this fantasy-adventure story, David, 13 years old, and his 10-year-old sister Jessica have been sent to their grandparents' farm in BC's Cariboo region. Their parents have recently separated and both children are in need of a rest and healing.
Soon after their arrival, Grandpa shows them a very special book "a large, ancient-looking book", with a lock. Inside the book is a "picture of two children standing on a path in the middle of a dark and misty forest." Underneath are the cryptic worlds:
WHEN LOST IN THE MYSTERIOUS FOREST
THROUGH ENEMY LAND HE RIDES
CALL FOR HIM AND HE WILL BE
THE LIGHT WHERE DARKNESS HIDES.
On the other page is the picture of a man surrounded by brightness, astride a beautiful white horse. As the children gaze upon this picture, they are suddenly transported to the land of Antoch, on a distant planet, where an evil king has taken over the land. The children are then enlisted to assist "The Ryder" to take back the kingdom for Himself and restore peace, love, and harmony to His people.