When bikes begin to go missing in their neighborhood, The Sycamore Detective Agency is on the case. They set a trap for the thieves, but the detectives must be careful... careful not to get caught by their parents. Headquartered in the historic and mysterious farmhouse known as Barton Manor, nine-year-old Johnny Smith and his younger brothers Matt and Cooper secretly fight crime in Rocklin, California with the help of their adventure-loving grandfather. Bonnie and Clyde, the thieves that have the police stumped, have been stealing kids' bikes all over town. Grandpa Jack and the boys plot and plan between baseball games and homework about how to put the pair of thieves away for good, and how to do it without their parents finding out. Will Johnny, Matt, and Coop help Chief Mulligan put the thieves behind bars, or will Mr. and Mrs. Smith find out what their boys are up to and close down The Sycamore Detective Agency for good?