[1] Fatty is made the leader of the Five Find-Outers, after he explains that he has been studying how to get out of a locked room when the key is not on his side, to write letters with invisible ink (or orange/lemon juice) and has been practising disguises.

Pip disguises himself with a wig and some false teeth and attracts the attention of Mr Goon, who chases him across the village.

The children trace the owner of the house to a "John Henry Smith", who lives in a distant town.

However, he is captured by the men (who are foreigners) and forced to write a letter to the other children, to trap them inside the house.

Meanwhile, Fatty escapes from a locked room and manages to meet Inspector Jenks outside the house and hand him the code book, after which the police round up the villains, who are international thieves.