Commando Raid (I) - S1.E13

In the barn at Secret Valley, the doctor and children decode the latest cryptogram. Matt however is listening outside and when the others leave the barn, he creeps inside and takes a copy of the decoded message. He is disturbed by the others, but not before he has planted a listening bug under the table, which Dingle is tuned in to, nearby. The lookout sees Dingle's car and Sparks decides to investigate. He discovers Dingle and learns that the barn is bugged. He runs back to warn the others. They find the bug and send Dingle in a different direction by giving him a false lead. The doctor and children leave the camp to search for the next salamander and mineral.