The sleuthing son of a Des Moines police detective assists his father in nabbing a notorious jewel thief after transforming his clubhouse into the Junior Detective Agency. There's no one in the world that Sam Steele, Jr. admires more than his father, and lately Sam, Sr. has been on the trail of a crafty burglar who calls himself The Cat. Convinced that it's finally time to make the leap to the big leagues, Sam, Jr. begins looking over the evidence, and hires local tween Emma Marsh as his receptionist. Emma's loyal canine Doug has the perfect nose for sniffing out crime, and after a few weeks of fruitless stakeouts he leads Emma and Sam, Jr. straight to The Cat. The Cat locks up Sam, Jr. and Doug in a dingy warehouse, it starts to look like he'll escape scot free. But the one person The Cat didn't count on was Emma, who quickly recruits Sam, Sr. to help out the elusive thief away once and for all.