The Boxes (Electronic book text)

Annie's Uncle Marco goes on one of his mysterious trips, leaving her in charge of two sealed boxes on one condition: she must not open either one while he is away. But she is tempted...and soon she has unleashed the unspeakable. The creatures inside the box are crab-like and grotesque. And they possess a power Annie could never have imagined: the power to transmute time. "Sleator is the master of the creepy-crawly, and his inventiveness is at full power here." --The Horn Book