*** NEW free study guide written by the author: www.kristianagregory.com *** Lost Island was off limits -- until now. Jeff and David are going to the desert island to search for clues. And hidden treasure Town legend tells of a robber and a secret cave, but the brothers have to piece the truth together. With the help of their cousin, Claire, they'll get to the bottom of the mystery, no matter what they have to dig up.

It's the middle of the night when Jeff spots someone dumping a large bundle into the lake. It's too dark to identify anyone -- or anything. But the cousins immediately suspect foul play, and plunge right into the mystery. Before they know it, the kids of Cabin Creek are in too deep. Everyone is a suspect -- and the cousins are all in danger.

When a camper disappears from the dangerous lookout at Skull Cliff, the cousins wonder if it is the old town curse at work. Then the police discover a ransom note, and everyone is in search of a kidnaper. But Jeff, David, and Claire can't make the clues fit. Was the bossy boy from the city kidnapped, or did something even spookier take place on Skull Cliff?

During summer vacation the cousins are excited to visit their grandparents on Hidden Horse Ranch. They get to sleep in a bunkhouse, swim in a pond with a rope swing, and ride horses any time they want. But they arrive to find that a mysterious fire has destroyed the stables, and the herd has escaped into the nearby canyons. Also troubling, valuable objects have been disappearing from the ranch house. As Jeff, David, and Claire follow clues and suspects, they keep running into dead-ends and wonder if the ranch has a phantom.

When a girl's face appears, then disappears, outside a window of their spooky old schoolhouse, the cousins think they've seen a ghost. More strange clues -- piano music lilting through empty halls, a secret passageway, and an old portrait that looks like the girl from the window -- make Jeff, David, and Claire begin to wonder: Is their school just spooky, or could it be ... haunted?

Jeff, David, and Claire love their winter break jobs at the ski chalet on Blue Mountain, where they get to snowboard and go sledding between shifts of cleaning and tending to the grounds. But when things start going missing from the chalet, the cousins find themselves prime suspects. Can they solve the mystery before they get ski-lifted out of their winter wonderland? Or will trying to solve the case make them the frosty culprit's next target?

The cousins discover a mysterious stranger sneaking into the local dump. When bikes, toasters, and other items disappear all over town, they begin to suspect he might be up to no good. But when these items show up again, fixed and freshly painted, Jeff, David, and Claire are confused. What kind of thief repairs and returns his stolen goods?