When Julian, Sarah, and Peter arrive at the crumbling Hollowbrook Mansion for what they think will be a boring few weeks watching their father repair antique clocks, they have no idea they're about to stumble into the mystery of a lifetime.

Strange thumping sounds echo through the night-sometimes from below the mansion, sometimes from just outside their windows. The estate's gardener, Mr. Griggs, guards an old garden shed like it holds the crown jewels, warning the children to stay away with barely concealed threats. And valuable antiques that their father carefully catalogs seem to be disappearing without a trace.

Determined to solve the puzzle, the three siblings begin their own investigation. What they discover hidden beneath the innocent-looking shed will lead them on a dangerous adventure through secret underground tunnels, put them face-to-face with cunning thieves, and test their courage in ways they never imagined.

Can three kids outsmart a pair of ruthless criminals? Will they escape the locked cellar before it's too late? And what other secrets does Hollowbrook Mansion hold in its shadowy depths?

Perfect for readers who love mysteries, adventure, and stories where clever kids save the day, "The Garden Shed Secret will keep young readers turning pages late into the night-just like Julian, Sarah, and Peter listening for those mysterious thumps in the dark.