Twins Maggie and Jennifer aren't looking for another mystery when they join the girls' adventurous grandmother on a Mexican holiday. Then they run into the crooks... and the gun runners...and the CIA agent. "Grand" has planned the best holiday ever, and it's more than just sitting around on glamorous beaches. The kids are going to see the architectural wonders of Mexico, from the beautiful Temple of Venus at Uxmal, with its wonderful carved facade, to the mysterious Temple of the Magician. On this trip, the kids won't need to make use of Jennifer's marvellous talent - the ability to become invisible - because there won't be a mystery to solve or trouble to escape. That part of their life is done with. But Grand and espionage are never far apart, and soon the kids are drawn back into a world of deadly intrigue, struggling to make sense of the perilous world unfolding around them. Grand herself is used to danger, of course. Even so, no one bargained on murder. In broad daylight. Soon Jennifer's magical gift is needed again as a terrifying game of cat and mouse plays out at the Temple of the Magician. If the kids aren't careful, one of them might not be coming home from the holidays.