Low Tide at Tybee — James M. Jackson

In  the novella "Low Tide at Tybee," Seamus McCree,  his darts-throwing mother, and his now six-year-old granddaughter, Megan, vacation on Tybee Island, Georgia to escape winter up north.

Megan spots a thief going through their beach bags, after which their vacation unravels with a series of twists and turns that will leave you guessing until the end, trying to figure out who done what.