Three children making a map of all the interesting places around their seaside village stumble upon a group of suspicious-acting gents and begin to investigate their activities. Turns out they're a gang of smugglers who use a recurring cat motif in all their plans. With the help of one of the children's uncle Dobbs, Tug Wilson, a boat captain friend of theirs, and some Customs officers, the children make sure "The Cat Gang" are eventually brought to justice.
—wiseguy-18