Twinter: The First Portal. Bede Series, #1

Ghosts, time-travel, a dozen impossible riddles, and a curse of snowTwelve-year-old twins, Kit (a keen boy-scientist) and Bash (a girl with a natural 'green thumb' and a flair for elaborate words) are excited to be moving from a noisy city to Bede Hall, their eccentric grandmother's crumbling stately home, set in the sleepy English countryside. With all that's gone horribly wrong for a year, moving to a grand old mansion seems a solution that promises an adventure of endless exploration and freedom.
Bash can create the garden of her dreams and Kit has an abandoned space to set up his own laboratory. Instead, they stumble upon a portal to the future with three disturbing secrets, begin to untangle the supernatural history of Bede - a village as bizarre as their grandmother's magic snow globe, and meet some unexpected life-forms who appear to be as haunted as the ghost of Bede Hall - a hapless young girl trapped in the attic's 'wintry room'.
In order to save the planet, the twins must navigate a maze of time portals to unravel an age-old mystery. The answers lie in Ancient Egypt, but only time will surrender its hidden knowledge, and according to their grandmother's old hourglass, time is running out. Holding the world in one's hands is a big responsibility