(IBList user synopsis):
Christmas holidays! But they seem to be boring. Fatty tries out several new disguises, until he stumbles on a house that is completely empty but for one room.
This time it seems that they are not able to solve the mystery, but when Fatty decides to investigate the house, things happen fast. Fatty doesn't return and Mr. Goon is also nowhere to be found. It is time the children act, and together with Inspector Jenkins they bring all to a good end.
Original title: the Mystery of the Secret Room
Genre: Fiction→ Children & Young Adult→ Mystery