When their father goes off to war, a group of children that includes the mischievous Robert (Freddie Highmore) and Cyril (Jonathan Bailey) stay with their uncle, who has a greenhouse on his property. There, they discover "It," a creature they recognize from bedtime stories as being a sand fairy. "It" can grant wishes -- but as the children and their cousin, Horace (Alexander Pownall), soon find out, the more outlandish their desire, the greater the chance for disaster to result.