From the series: Ollie and Emma stories

The Mysterious Door: Two siblings find adventure and danger in a parallel universe (The Adventures of Ollie and Emma Book 1)

About

 Emma’s day turned from sunshine to sadness. Kyle wasn’t where he said he’d be but Shawna was. She’d been taunting Emma all year and today was more of the same. Add to that, Emma’s best friend, Cindy, had joined in the jeering!

Humiliated, her heart shattered into tiny bits of glass. To ease the pain, she and Ollie, her brother, go for a run in the forest behind their house. There they find an old tree with a mysterious door. They open it to find a magical land filled with wondrous creatures. But, why did the door appear now? Can anyone here help Emma with her problems? There are some who like and welcome them and who want to help, but there are others who hate humans and want them caught. There isn’t time to get the help they need! They need to get home, but can they? The hunt is on. Will they be able to find their way back or are they doomed to be captured before they reach the door in the tree?