Radish and Stefy's father punishes them to stay at home and study math until Radish passes his exam. However, they skip the punishment to help their Grandpa, as someone has tricked him and run away with his money. It turns to be a school friend of their parent, Mr. Lehman. The investigation lead by Charly & Co involves Fred's Mum as an undercover agent to trick on Lehman! However, the smokescreen does not work and they find themselves interfering in previous police investigations.