Witch's Valley. Sapphire City Series, #5

Drew and his sister, Scarlett, never imagined being driven from their home. But when their cunning stepmother convinces their father they can't provide for them through the harsh winter; they're abandoned in the valley to fend for themselves. Determined not to give up, they find their way back, guided by a trail of small, white stones Drew left behind. What awaits them upon their return is far from what they hoped: a father who no longer remembers them, a stepmother hiding a dark and terrible secret, and a storehouse full of food they were told didn't exist.
Their stepmother isn't the woman she pretends to be, and now Drew and Scarlett must find a way to save their father from her clutches. Their only hope lies in the depths of the Witch's Valley, where a powerful witch might hold the key to defeating the creature that has taken over their lives.  As they journey into the valley, they encounter unexpected allies and dangerous foes. Discovering that not everything-or everyone-is as it seems.