 When Dr. Hugo Robbin s laboratory is blown up, his nurse Ann Loring is charged with murdering the doctor. During her trial, a group of children continually disrupts the courtroom, claiming to have important evidence. The children are finally allowed to testify, but as a result of their testimony, their friend Dan, who runs a repair shop, is now charged with the crime instead of the nurse. The children are now determined to prove Dan s innocence, and they go to the abandoned laboratory to look for evidence, leading to a series of hazardous adventures.