Mischievous Mercurio guards the planet Mercury-his sacred charge-with quirky devotion. He loves the oddball chunk of rock, with its illusion of retrograde motion and its out-of-sync orbit and spin. Almost as much as he loves playing pranks. But when Earth's guardian Gaia bids Mercurio to organize a circus act for Sol's birthday celebration, the joke's on him. While Mercurio wangles his way around the captious refusals of his...